[ios, macos] Updated documentation, tests, demo apps

25 files changed, 373 insertions, 373 deletions

diff --git a/platform/darwin/docs/guides/For Style Authors.md.ejs b/platform/darwin/docs/guides/For Style Authors.md.ejs
index 2ba7757fdf..d10aa58d56 100644
--- a/platform/darwin/docs/guides/For Style Authors.md.ejs
+++ b/platform/darwin/docs/guides/For Style Authors.md.ejs
@@ -330,8 +330,8 @@ In style specification | Method, function, or predicate type | Format string syn
 `string`               | |
 `to-boolean`           | `boolValue` |
 `to-color`             | |
-`to-number`            | `mgl_numberWithFallbackValues:` |
-`to-string`            | `stringValue` |
+`to-number`            | `mgl_numberWithFallbackValues:` | `CAST(zipCode, 'NSNumber')`
+`to-string`            | `stringValue` | `CAST(ele, 'NSString')`
 `typeof`               | |
 `geometry-type`        | |
 `id`                   | |
@@ -352,11 +352,11 @@ In style specification | Method, function, or predicate type | Format string syn
 `case`                 | `+[NSExpression expressionForConditional:trueExpression:falseExpression:]` | `TERNARY(condition, trueExpression, falseExpression)`
 `coalesce`             | |
 `match`                | |
-`interpolate`          | `mgl_interpolateWithCurveType:parameters:stops:` |
-`step`                 | `mgl_stepWithMinimum:stops:` |
-`let`                  | `mgl_expressionWithContext:` |
+`interpolate`          | `mgl_interpolate:withCurveType:parameters:stops:` |
+`step`                 | `mgl_step:withMinimum:stops:` |
+`let`                  | `mgl_expressionWithContext:` | `MGL_LET('ios', 11, 'macos', 10.13, $ios + $macos)`
 `var`                  | `+[NSExpression expressionForVariable:]` | `$variable`
-`concat`               | `stringByAppendingString:` |
+`concat`               | `mgl_join:` | `mgl_join({'Old', ' ', 'MacDonald'})`
 `downcase`             | `lowercase:` | `lowercase('DOWNTOWN')`
 `upcase`               | `uppercase:` | `uppercase('Elysian Fields')`
 <% if (macOS) { -%>
diff --git a/platform/darwin/docs/guides/Predicates and Expressions.md b/platform/darwin/docs/guides/Predicates and Expressions.md
index fd0f82c0eb..538aa2b850 100644
--- a/platform/darwin/docs/guides/Predicates and Expressions.md
+++ b/platform/darwin/docs/guides/Predicates and Expressions.md
@@ -192,7 +192,7 @@ string syntax:
 
 Initializer parameter | Format string syntax | Description
 ----------------------|----------------------|------------
-`mgl_interpolate:withCurveType:parameters:stops:` | `mgl_interpolate:withCurveType:parameters:stops:($zoom, 'linear', x, nil, %@)` | Produces continuous, smooth results by interpolating between pairs of input and output values (“stops”). Compared to the `mgl_interpolateWithCurveType:parameters:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
+`mgl_interpolate:withCurveType:parameters:stops:` | `mgl_interpolate:withCurveType:parameters:stops:(x, 'linear', nil, %@)` | Produces continuous, smooth results by interpolating between pairs of input and output values (“stops”). Compared to the `mgl_interpolateWithCurveType:parameters:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
 `mgl_step:from:stops:` | `mgl_step:from:stops:(x, 11, %@)` |Produces discrete, stepped results by evaluating a piecewise-constant function defined by pairs of input and output values ("stops"). Compared to the `mgl_stepWithMinimum:stops:` custom function, the input expression (that function’s target) is instead passed in as the first argument to this function.
 `mgl_join:` | `mgl_join({'Old', 'MacDonald'})` | Returns the result of concatenating together all the elements of an array in order. Compared to the `stringByAppendingString:` custom function, this function takes only one argument, which is an aggregate expression containing the strings to concatenate.
 `MGL_LET` | `MGL_LET('age', uppercase('old'), 'name', uppercase('MacDonald'), mgl_join({$age, $name}))` | Any number of variable names interspersed with their assigned `NSExpression` values, followed by an `NSExpression` that may contain references to those variables. Compared to the `mgl_expressionWithContext:` custom function, this function takes the variable names and values inline before the expression that contains references to those variables.
diff --git a/platform/darwin/src/MGLCircleStyleLayer.h b/platform/darwin/src/MGLCircleStyleLayer.h
index 2523637179..aa2d07db26 100644
--- a/platform/darwin/src/MGLCircleStyleLayer.h
+++ b/platform/darwin/src/MGLCircleStyleLayer.h
@@ -83,7 +83,7 @@ typedef NS_ENUM(NSUInteger, MGLCircleTranslationAnchor) {
  let layer = MGLCircleStyleLayer(identifier: "circles", source: population)
  layer.sourceLayerIdentifier = "population"
  layer.circleColor = NSExpression(forConstantValue: UIColor.green)
- layer.circleRadius = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.75, %@)",
+ layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.75, %@)",
                                    [12: 2,
                                     22: 180])
  layer.circleOpacity = NSExpression(forConstantValue: 0.7)
diff --git a/platform/darwin/src/MGLHeatmapStyleLayer.h b/platform/darwin/src/MGLHeatmapStyleLayer.h
index ff2b92f226..1c68e2cae8 100644
--- a/platform/darwin/src/MGLHeatmapStyleLayer.h
+++ b/platform/darwin/src/MGLHeatmapStyleLayer.h
@@ -35,10 +35,10 @@ NS_ASSUME_NONNULL_BEGIN
 
  ```swift
  let layer = MGLHeatmapStyleLayer(identifier: "earthquake-heat", source: earthquakes)
- layer.heatmapWeight = NSExpression(format: "FUNCTION(magnitude, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+ layer.heatmapWeight = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(magnitude, 'linear', nil, %@)",
                                     [0: 0,
                                      6: 1])
- layer.heatmapIntensity = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+ layer.heatmapIntensity = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                        [0: 1,
                                         9: 3])
  mapView.style?.addLayer(layer)
diff --git a/platform/darwin/src/MGLLineStyleLayer.h b/platform/darwin/src/MGLLineStyleLayer.h
index bdb5464ebc..d8e109d559 100644
--- a/platform/darwin/src/MGLLineStyleLayer.h
+++ b/platform/darwin/src/MGLLineStyleLayer.h
@@ -93,7 +93,7 @@ typedef NS_ENUM(NSUInteger, MGLLineTranslationAnchor) {
  ```swift
  let layer = MGLLineStyleLayer(identifier: "trails-path", source: trails)
  layer.sourceLayerIdentifier = "trails"
- layer.lineWidth = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+ layer.lineWidth = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.5, %@)",
                                 [14: 2,
                                  18: 20])
  layer.lineColor = NSExpression(forConstantValue: UIColor.brown)
diff --git a/platform/darwin/src/MGLStyleValue.h b/platform/darwin/src/MGLStyleValue.h
index f6e9c51729..65f89c5909 100644
--- a/platform/darwin/src/MGLStyleValue.h
+++ b/platform/darwin/src/MGLStyleValue.h
@@ -8,13 +8,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 typedef NSString *MGLStyleFunctionOption NS_STRING_ENUM NS_UNAVAILABLE;
 
-extern MGL_EXPORT const MGLStyleFunctionOption MGLStyleFunctionOptionInterpolationBase __attribute__((unavailable("Use NSExpression instead, applying the mgl_interpolateWithCurveType:parameters:stops: function with a curve type of “exponential” and a non-nil parameter.")));
+extern MGL_EXPORT const MGLStyleFunctionOption MGLStyleFunctionOptionInterpolationBase __attribute__((unavailable("Use NSExpression instead, applying the mgl_interpolate:withCurveType:parameters:stops: function with a curve type of “exponential” and a non-nil parameter.")));
 
 extern MGL_EXPORT const MGLStyleFunctionOption MGLStyleFunctionOptionDefaultValue __attribute__((unavailable("Use +[NSExpression expressionForConditional:trueExpression:falseExpression:] instead.")));
 
 typedef NS_ENUM(NSUInteger, MGLInterpolationMode) {
-    MGLInterpolationModeExponential __attribute__((unavailable("Use NSExpression instead, applying the mgl_interpolateWithCurveType:parameters:stops: function with a curve type of “exponential”."))) = 0,
-    MGLInterpolationModeInterval __attribute__((unavailable("Use NSExpression instead, calling the mgl_stepWithMinimum:stops: function."))),
+    MGLInterpolationModeExponential __attribute__((unavailable("Use NSExpression instead, applying the mgl_interpolate:withCurveType:parameters:stops: function with a curve type of “exponential”."))) = 0,
+    MGLInterpolationModeInterval __attribute__((unavailable("Use NSExpression instead, calling the mgl_step:from:stops: function."))),
     MGLInterpolationModeCategorical __attribute__((unavailable("Use NSExpression instead."))),
     MGLInterpolationModeIdentity __attribute__((unavailable("Use +[NSExpression expressionForKeyPath:] instead.")))
 } __attribute__((unavailable("Use NSExpression instead.")));
@@ -29,19 +29,19 @@ MGL_EXPORT __attribute__((unavailable("Use +[NSExpression expressionForConstantV
 
 @compatibility_alias MGLStyleConstantValue MGLConstantStyleValue;
 
-MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, calling the mgl_stepWithMinimum:stops: or mgl_interpolateWithCurveType:parameters:stops: function.")))
+MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, calling the mgl_step:from:stops: or mgl_interpolate:withCurveType:parameters:stops: function.")))
 @interface MGLStyleFunction<T> : MGLStyleValue<T>
 @end
 
-MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, applying the mgl_stepWithMinimum:stops: or mgl_interpolateWithCurveType:parameters:stops: function to the $zoomLevel variable.")))
+MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, applying the mgl_step:from:stops: or mgl_interpolate:withCurveType:parameters:stops: function to the $zoomLevel variable.")))
 @interface MGLCameraStyleFunction<T> : MGLStyleFunction<T>
 @end
 
-MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, applying the mgl_stepWithMinimum:stops: or mgl_interpolateWithCurveType:parameters:stops: function to a key path expression.")))
+MGL_EXPORT __attribute__((unavailable("Use NSExpression instead, applying the mgl_step:from:stops: or mgl_interpolate:withCurveType:parameters:stops: function to a key path expression.")))
 @interface MGLSourceStyleFunction<T> : MGLStyleFunction<T>
 @end
 
-MGL_EXPORT __attribute__((unavailable("Use a NSExpression instead with nested mgl_stepWithMinimum:stops: or mgl_interpolateWithCurveType:parameters:stops: function calls.")))
+MGL_EXPORT __attribute__((unavailable("Use a NSExpression instead with nested mgl_step:from:stops: or mgl_interpolate:withCurveType:parameters:stops: function calls.")))
 @interface MGLCompositeStyleFunction<T> : MGLStyleFunction<T>
 @end
 
diff --git a/platform/darwin/test/MGLBackgroundStyleLayerTests.mm b/platform/darwin/test/MGLBackgroundStyleLayerTests.mm
index e7c2982413..de8080f425 100644
--- a/platform/darwin/test/MGLBackgroundStyleLayerTests.mm
+++ b/platform/darwin/test/MGLBackgroundStyleLayerTests.mm
@@ -42,7 +42,7 @@
                               @"backgroundColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.backgroundColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -66,8 +66,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.backgroundColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.backgroundColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.backgroundColorTransition = transitionTest;
@@ -95,7 +95,7 @@
                               @"backgroundOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.backgroundOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -119,8 +119,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.backgroundOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.backgroundOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.backgroundOpacityTransition = transitionTest;
@@ -148,7 +148,7 @@
                               @"backgroundPattern should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Background Pattern'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.backgroundPattern = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -172,8 +172,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.backgroundPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.backgroundPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLBackgroundLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.backgroundPatternTransition = transitionTest;
diff --git a/platform/darwin/test/MGLCircleStyleLayerTests.mm b/platform/darwin/test/MGLCircleStyleLayerTests.mm
index 7677344580..cb950a1feb 100644
--- a/platform/darwin/test/MGLCircleStyleLayerTests.mm
+++ b/platform/darwin/test/MGLCircleStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"circleBlur should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleBlur = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -77,7 +77,7 @@
         XCTAssertEqualObjects(layer.circleBlur, functionExpression,
                               @"circleBlur should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleBlur = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -88,7 +88,7 @@
         XCTAssertEqualObjects(layer.circleBlur, functionExpression,
                               @"circleBlur should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleBlur = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -133,7 +133,7 @@
                               @"circleColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -147,7 +147,7 @@
         XCTAssertEqualObjects(layer.circleColor, functionExpression,
                               @"circleColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -158,7 +158,7 @@
         XCTAssertEqualObjects(layer.circleColor, functionExpression,
                               @"circleColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -203,7 +203,7 @@
                               @"circleOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -217,7 +217,7 @@
         XCTAssertEqualObjects(layer.circleOpacity, functionExpression,
                               @"circleOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -228,7 +228,7 @@
         XCTAssertEqualObjects(layer.circleOpacity, functionExpression,
                               @"circleOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -273,7 +273,7 @@
                               @"circlePitchAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circlePitchAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::AlignmentType> intervalStops = {{
@@ -297,8 +297,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.circlePitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.circlePitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -317,7 +317,7 @@
                               @"circleRadius should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleRadius = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -331,7 +331,7 @@
         XCTAssertEqualObjects(layer.circleRadius, functionExpression,
                               @"circleRadius should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleRadius = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -342,7 +342,7 @@
         XCTAssertEqualObjects(layer.circleRadius, functionExpression,
                               @"circleRadius should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleRadius = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -387,7 +387,7 @@
                               @"circleScaleAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleScaleAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::CirclePitchScaleType> intervalStops = {{
@@ -411,8 +411,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.circleScaleAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.circleScaleAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -431,7 +431,7 @@
                               @"circleStrokeColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleStrokeColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -445,7 +445,7 @@
         XCTAssertEqualObjects(layer.circleStrokeColor, functionExpression,
                               @"circleStrokeColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleStrokeColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -456,7 +456,7 @@
         XCTAssertEqualObjects(layer.circleStrokeColor, functionExpression,
                               @"circleStrokeColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleStrokeColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -501,7 +501,7 @@
                               @"circleStrokeOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleStrokeOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -515,7 +515,7 @@
         XCTAssertEqualObjects(layer.circleStrokeOpacity, functionExpression,
                               @"circleStrokeOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleStrokeOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -526,7 +526,7 @@
         XCTAssertEqualObjects(layer.circleStrokeOpacity, functionExpression,
                               @"circleStrokeOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleStrokeOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -571,7 +571,7 @@
                               @"circleStrokeWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleStrokeWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -585,7 +585,7 @@
         XCTAssertEqualObjects(layer.circleStrokeWidth, functionExpression,
                               @"circleStrokeWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.circleStrokeWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -596,7 +596,7 @@
         XCTAssertEqualObjects(layer.circleStrokeWidth, functionExpression,
                               @"circleStrokeWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.circleStrokeWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -647,7 +647,7 @@
                               @"circleTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -671,8 +671,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.circleTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.circleTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -691,7 +691,7 @@
                               @"circleTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.circleTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -715,8 +715,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.circleTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.circleTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLCircleLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 }
diff --git a/platform/darwin/test/MGLDocumentationExampleTests.swift b/platform/darwin/test/MGLDocumentationExampleTests.swift
index a216d9ad1c..5a112f07e2 100644
--- a/platform/darwin/test/MGLDocumentationExampleTests.swift
+++ b/platform/darwin/test/MGLDocumentationExampleTests.swift
@@ -162,7 +162,7 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         #else
             layer.circleColor = NSExpression(forConstantValue: UIColor.green)
         #endif
-        layer.circleRadius = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.75, %@)",
+        layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.75, %@)",
                                           [12: 2,
                                            22: 180])
         layer.circleOpacity = NSExpression(forConstantValue: 0.7)
@@ -180,7 +180,7 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         //#-example-code
         let layer = MGLLineStyleLayer(identifier: "trails-path", source: trails)
         layer.sourceLayerIdentifier = "trails"
-        layer.lineWidth = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+        layer.lineWidth = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.5, %@)",
                                        [14: 2,
                                         18: 20])
         #if os(macOS)
@@ -237,10 +237,10 @@ class MGLDocumentationExampleTests: XCTestCase, MGLMapViewDelegate {
         
         //#-example-code
         let layer = MGLHeatmapStyleLayer(identifier: "earthquake-heat", source: earthquakes)
-        layer.heatmapWeight = NSExpression(format: "FUNCTION(magnitude, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+        layer.heatmapWeight = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(magnitude, 'linear', nil, %@)",
                                            [0: 0,
                                             6: 1])
-        layer.heatmapIntensity = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+        layer.heatmapIntensity = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                               [0: 1,
                                                9: 3])
         mapView.style?.addLayer(layer)
diff --git a/platform/darwin/test/MGLDocumentationGuideTests.swift b/platform/darwin/test/MGLDocumentationGuideTests.swift
index f939695f32..8769bc4428 100644
--- a/platform/darwin/test/MGLDocumentationGuideTests.swift
+++ b/platform/darwin/test/MGLDocumentationGuideTests.swift
@@ -71,7 +71,7 @@ class MGLDocumentationGuideTests: XCTestCase, MGLMapViewDelegate {
         #endif
         //#-end-example-code
         
-        let _ = NSExpression(format: "FUNCTION(mag, 'mgl_stepWithMinimum:stops:', %@, %@)",
+        let _ = NSExpression(format: "mgl_step:from:stops:(mag, %@, %@)",
                              stops[0]!, stops)
     }
     
@@ -104,10 +104,10 @@ class MGLDocumentationGuideTests: XCTestCase, MGLMapViewDelegate {
         
         let layer = MGLCircleStyleLayer(identifier: "circles", source: source)
         #if os(macOS)
-            layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+            layer.circleColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)",
                                              stops)
         #else
-            layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+            layer.circleColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)",
                                              stops)
         #endif
         layer.circleRadius = NSExpression(forConstantValue: 10)
@@ -126,7 +126,7 @@ class MGLDocumentationGuideTests: XCTestCase, MGLMapViewDelegate {
             18: 18,
         ]
         
-        layer.circleRadius = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+        layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.5, %@)",
                                           stops)
         //#-end-example-code
     }
@@ -145,7 +145,7 @@ class MGLDocumentationGuideTests: XCTestCase, MGLMapViewDelegate {
                 10: .white,
             ]
             
-            layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_stepWithMinimum:stops:', %@, %@)",
+            layer.circleColor = NSExpression(format: "mgl_step:from:stops:(mag, %@, %@)",
                                              NSColor.green, stops)
         #else
             let stops: [Float: UIColor] = [
@@ -156,7 +156,7 @@ class MGLDocumentationGuideTests: XCTestCase, MGLMapViewDelegate {
                 10: .white,
             ]
             
-            layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_stepWithMinimum:stops:', %@, %@)",
+            layer.circleColor = NSExpression(format: "mgl_step:from:stops:(mag, %@, %@)",
                                              UIColor.green, stops)
         #endif
         //#-end-example-code
diff --git a/platform/darwin/test/MGLFillExtrusionStyleLayerTests.mm b/platform/darwin/test/MGLFillExtrusionStyleLayerTests.mm
index f5e26381d6..876386948c 100644
--- a/platform/darwin/test/MGLFillExtrusionStyleLayerTests.mm
+++ b/platform/darwin/test/MGLFillExtrusionStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"fillExtrusionBase should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionBase = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -77,7 +77,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionBase, functionExpression,
                               @"fillExtrusionBase should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillExtrusionBase = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -88,7 +88,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionBase, functionExpression,
                               @"fillExtrusionBase should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillExtrusionBase = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -133,7 +133,7 @@
                               @"fillExtrusionColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -147,7 +147,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionColor, functionExpression,
                               @"fillExtrusionColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillExtrusionColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -158,7 +158,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionColor, functionExpression,
                               @"fillExtrusionColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillExtrusionColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -203,7 +203,7 @@
                               @"fillExtrusionHeight should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionHeight = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -217,7 +217,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionHeight, functionExpression,
                               @"fillExtrusionHeight should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillExtrusionHeight = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -228,7 +228,7 @@
         XCTAssertEqualObjects(layer.fillExtrusionHeight, functionExpression,
                               @"fillExtrusionHeight should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillExtrusionHeight = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -273,7 +273,7 @@
                               @"fillExtrusionOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -297,8 +297,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.fillExtrusionOpacityTransition = transitionTest;
@@ -326,7 +326,7 @@
                               @"fillExtrusionPattern should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Fill Extrusion Pattern'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionPattern = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -350,8 +350,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.fillExtrusionPatternTransition = transitionTest;
@@ -385,7 +385,7 @@
                               @"fillExtrusionTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -409,8 +409,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -429,7 +429,7 @@
                               @"fillExtrusionTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillExtrusionTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -453,8 +453,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillExtrusionTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillExtrusionLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 }
diff --git a/platform/darwin/test/MGLFillStyleLayerTests.mm b/platform/darwin/test/MGLFillStyleLayerTests.mm
index 25521f3ede..8fa349c135 100644
--- a/platform/darwin/test/MGLFillStyleLayerTests.mm
+++ b/platform/darwin/test/MGLFillStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"fillAntialiased should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"false"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillAntialiased = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -87,8 +87,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillAntialiased = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillAntialiased = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -107,7 +107,7 @@
                               @"fillColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -121,7 +121,7 @@
         XCTAssertEqualObjects(layer.fillColor, functionExpression,
                               @"fillColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -132,7 +132,7 @@
         XCTAssertEqualObjects(layer.fillColor, functionExpression,
                               @"fillColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -177,7 +177,7 @@
                               @"fillOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -191,7 +191,7 @@
         XCTAssertEqualObjects(layer.fillOpacity, functionExpression,
                               @"fillOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -202,7 +202,7 @@
         XCTAssertEqualObjects(layer.fillOpacity, functionExpression,
                               @"fillOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -247,7 +247,7 @@
                               @"fillOutlineColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillOutlineColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -261,7 +261,7 @@
         XCTAssertEqualObjects(layer.fillOutlineColor, functionExpression,
                               @"fillOutlineColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.fillOutlineColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -272,7 +272,7 @@
         XCTAssertEqualObjects(layer.fillOutlineColor, functionExpression,
                               @"fillOutlineColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.fillOutlineColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -317,7 +317,7 @@
                               @"fillPattern should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Fill Pattern'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillPattern = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -341,8 +341,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.fillPatternTransition = transitionTest;
@@ -376,7 +376,7 @@
                               @"fillTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -400,8 +400,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -420,7 +420,7 @@
                               @"fillTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.fillTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -444,8 +444,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.fillTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.fillTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLFillLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 }
diff --git a/platform/darwin/test/MGLHeatmapColorTests.mm b/platform/darwin/test/MGLHeatmapColorTests.mm
index 8d44064d94..ba28cc0345 100644
--- a/platform/darwin/test/MGLHeatmapColorTests.mm
+++ b/platform/darwin/test/MGLHeatmapColorTests.mm
@@ -33,7 +33,7 @@
 
     constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
     NSExpression *constantExpression2 = [NSExpression expressionWithFormat:@"%@", [MGLColor blueColor]];
-    NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($heatmapDensity, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@12: constantExpression2}];
+    NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($heatmapDensity, %@, %@)", constantExpression, @{@12: constantExpression2}];
     layer.heatmapColor = functionExpression;
     
     XCTAssertEqual(rawLayer->getHeatmapColor().evaluate(11.0), mbgl::Color::red(),
@@ -49,12 +49,12 @@
     XCTAssertEqualObjects(layer.heatmapColor, defaultExpression,
                           @"heatmapColor should return the default value after being unset.");
 
-    functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+    functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
     XCTAssertThrowsSpecificNamed(layer.heatmapColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera expression is applied to heatmapColor.");
     functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
     XCTAssertThrowsSpecificNamed(layer.heatmapColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a data expression is applied to heatmapColor.");
-    functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-    functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+    functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+    functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
     XCTAssertThrowsSpecificNamed(layer.heatmapColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
 }
 
diff --git a/platform/darwin/test/MGLHeatmapStyleLayerTests.mm b/platform/darwin/test/MGLHeatmapStyleLayerTests.mm
index 74121affd8..4b51c6cc62 100644
--- a/platform/darwin/test/MGLHeatmapStyleLayerTests.mm
+++ b/platform/darwin/test/MGLHeatmapStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"heatmapIntensity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.heatmapIntensity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -87,8 +87,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.heatmapIntensity = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.heatmapIntensity = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.heatmapIntensityTransition = transitionTest;
@@ -116,7 +116,7 @@
                               @"heatmapOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.heatmapOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -140,8 +140,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.heatmapOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.heatmapOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLHeatmapLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.heatmapOpacityTransition = transitionTest;
@@ -169,7 +169,7 @@
                               @"heatmapRadius should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.heatmapRadius = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -183,7 +183,7 @@
         XCTAssertEqualObjects(layer.heatmapRadius, functionExpression,
                               @"heatmapRadius should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.heatmapRadius = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -194,7 +194,7 @@
         XCTAssertEqualObjects(layer.heatmapRadius, functionExpression,
                               @"heatmapRadius should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.heatmapRadius = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -239,7 +239,7 @@
                               @"heatmapWeight should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.heatmapWeight = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -253,7 +253,7 @@
         XCTAssertEqualObjects(layer.heatmapWeight, functionExpression,
                               @"heatmapWeight should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.heatmapWeight = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -264,7 +264,7 @@
         XCTAssertEqualObjects(layer.heatmapWeight, functionExpression,
                               @"heatmapWeight should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.heatmapWeight = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
diff --git a/platform/darwin/test/MGLHillshadeStyleLayerTests.mm b/platform/darwin/test/MGLHillshadeStyleLayerTests.mm
index b0b7ddd5ee..34937d1674 100644
--- a/platform/darwin/test/MGLHillshadeStyleLayerTests.mm
+++ b/platform/darwin/test/MGLHillshadeStyleLayerTests.mm
@@ -45,7 +45,7 @@
                               @"hillshadeAccentColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeAccentColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -69,8 +69,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeAccentColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeAccentColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.hillshadeAccentColorTransition = transitionTest;
@@ -98,7 +98,7 @@
                               @"hillshadeExaggeration should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeExaggeration = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -122,8 +122,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeExaggeration = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeExaggeration = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.hillshadeExaggerationTransition = transitionTest;
@@ -151,7 +151,7 @@
                               @"hillshadeHighlightColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeHighlightColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -175,8 +175,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeHighlightColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeHighlightColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.hillshadeHighlightColorTransition = transitionTest;
@@ -204,7 +204,7 @@
                               @"hillshadeIlluminationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeIlluminationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::HillshadeIlluminationAnchorType> intervalStops = {{
@@ -228,8 +228,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeIlluminationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeIlluminationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -248,7 +248,7 @@
                               @"hillshadeIlluminationDirection should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeIlluminationDirection = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -272,8 +272,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeIlluminationDirection = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeIlluminationDirection = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -292,7 +292,7 @@
                               @"hillshadeShadowColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.hillshadeShadowColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -316,8 +316,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.hillshadeShadowColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.hillshadeShadowColor = functionExpression, NSException, NSInvalidArgumentException, @"MGLHillshadeLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.hillshadeShadowColorTransition = transitionTest;
diff --git a/platform/darwin/test/MGLLineStyleLayerTests.mm b/platform/darwin/test/MGLLineStyleLayerTests.mm
index bf98e98320..bbc382567b 100644
--- a/platform/darwin/test/MGLLineStyleLayerTests.mm
+++ b/platform/darwin/test/MGLLineStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"lineCap should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'square'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineCap = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::LineCapType> intervalStops = {{
@@ -87,8 +87,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineCap = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineCap = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -107,7 +107,7 @@
                               @"lineJoin should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'miter'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineJoin = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::LineJoinType> intervalStops = {{
@@ -145,7 +145,7 @@
                               @"lineMiterLimit should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineMiterLimit = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -169,8 +169,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineMiterLimit = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineMiterLimit = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -189,7 +189,7 @@
                               @"lineRoundLimit should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineRoundLimit = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -213,8 +213,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineRoundLimit = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineRoundLimit = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -233,7 +233,7 @@
                               @"lineBlur should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineBlur = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -247,7 +247,7 @@
         XCTAssertEqualObjects(layer.lineBlur, functionExpression,
                               @"lineBlur should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineBlur = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -258,7 +258,7 @@
         XCTAssertEqualObjects(layer.lineBlur, functionExpression,
                               @"lineBlur should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineBlur = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -303,7 +303,7 @@
                               @"lineColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -317,7 +317,7 @@
         XCTAssertEqualObjects(layer.lineColor, functionExpression,
                               @"lineColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -328,7 +328,7 @@
         XCTAssertEqualObjects(layer.lineColor, functionExpression,
                               @"lineColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -373,7 +373,7 @@
                               @"lineDashPattern should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 2}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineDashPattern = functionExpression;
 
         mbgl::style::IntervalStops<std::vector<float>> intervalStops = {{
@@ -397,8 +397,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineDashPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineDashPattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -417,7 +417,7 @@
                               @"lineGapWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineGapWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -431,7 +431,7 @@
         XCTAssertEqualObjects(layer.lineGapWidth, functionExpression,
                               @"lineGapWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineGapWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -442,7 +442,7 @@
         XCTAssertEqualObjects(layer.lineGapWidth, functionExpression,
                               @"lineGapWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineGapWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -487,7 +487,7 @@
                               @"lineOffset should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineOffset = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -501,7 +501,7 @@
         XCTAssertEqualObjects(layer.lineOffset, functionExpression,
                               @"lineOffset should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineOffset = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -512,7 +512,7 @@
         XCTAssertEqualObjects(layer.lineOffset, functionExpression,
                               @"lineOffset should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineOffset = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -557,7 +557,7 @@
                               @"lineOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -571,7 +571,7 @@
         XCTAssertEqualObjects(layer.lineOpacity, functionExpression,
                               @"lineOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -582,7 +582,7 @@
         XCTAssertEqualObjects(layer.lineOpacity, functionExpression,
                               @"lineOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -627,7 +627,7 @@
                               @"linePattern should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Line Pattern'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.linePattern = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -651,8 +651,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.linePattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.linePattern = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.linePatternTransition = transitionTest;
@@ -686,7 +686,7 @@
                               @"lineTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -710,8 +710,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -730,7 +730,7 @@
                               @"lineTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -754,8 +754,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.lineTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.lineTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLLineLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -774,7 +774,7 @@
                               @"lineWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.lineWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -788,7 +788,7 @@
         XCTAssertEqualObjects(layer.lineWidth, functionExpression,
                               @"lineWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.lineWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -799,7 +799,7 @@
         XCTAssertEqualObjects(layer.lineWidth, functionExpression,
                               @"lineWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.lineWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
diff --git a/platform/darwin/test/MGLRasterStyleLayerTests.mm b/platform/darwin/test/MGLRasterStyleLayerTests.mm
index 5ded23ee3c..c8e454743e 100644
--- a/platform/darwin/test/MGLRasterStyleLayerTests.mm
+++ b/platform/darwin/test/MGLRasterStyleLayerTests.mm
@@ -45,7 +45,7 @@
                               @"maximumRasterBrightness should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.maximumRasterBrightness = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -69,8 +69,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.maximumRasterBrightness = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.maximumRasterBrightness = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -89,7 +89,7 @@
                               @"minimumRasterBrightness should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.minimumRasterBrightness = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -113,8 +113,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.minimumRasterBrightness = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.minimumRasterBrightness = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -133,7 +133,7 @@
                               @"rasterContrast should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.rasterContrast = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -157,8 +157,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.rasterContrast = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.rasterContrast = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.rasterContrastTransition = transitionTest;
@@ -186,7 +186,7 @@
                               @"rasterFadeDuration should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.rasterFadeDuration = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -210,8 +210,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.rasterFadeDuration = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.rasterFadeDuration = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -230,7 +230,7 @@
                               @"rasterHueRotation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.rasterHueRotation = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -254,8 +254,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.rasterHueRotation = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.rasterHueRotation = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -274,7 +274,7 @@
                               @"rasterOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.rasterOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -298,8 +298,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.rasterOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.rasterOpacity = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.rasterOpacityTransition = transitionTest;
@@ -327,7 +327,7 @@
                               @"rasterSaturation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.rasterSaturation = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -351,8 +351,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.rasterSaturation = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.rasterSaturation = functionExpression, NSException, NSInvalidArgumentException, @"MGLRasterLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
         // Transition property test
         layer.rasterSaturationTransition = transitionTest;
diff --git a/platform/darwin/test/MGLStyleLayerTests.mm.ejs b/platform/darwin/test/MGLStyleLayerTests.mm.ejs
index e17501ed18..ef4ffdb42e 100644
--- a/platform/darwin/test/MGLStyleLayerTests.mm.ejs
+++ b/platform/darwin/test/MGLStyleLayerTests.mm.ejs
@@ -80,7 +80,7 @@
                               @"<%- objCName(property) %> should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:<%- objCTestValue(property, type, false, 3) %>];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.<%- objCName(property) %> = functionExpression;
 
         mbgl::style::IntervalStops<<%- mbglType(property) %>> intervalStops = {{
@@ -95,7 +95,7 @@
                               @"<%- objCName(property) %> should round-trip camera expressions.");
 
 <% if (property["property-function"] && isInterpolatable(property)) { -%>
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.<%- objCName(property) %> = functionExpression;
 
         mbgl::style::ExponentialStops<<%- mbglType(property) %>> exponentialStops = { {{18, <%- mbglTestValue(property, type) %>}}, 1.0 };
@@ -106,7 +106,7 @@
         XCTAssertEqualObjects(layer.<%- objCName(property) %>, functionExpression,
                               @"<%- objCName(property) %> should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.<%- objCName(property) %> = functionExpression;
 
         std::map<float, <%- mbglType(property) %>> innerStops { {18, <%- mbglTestValue(property, type) %>} };
@@ -131,8 +131,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.<%- objCName(property) %> = functionExpression, NSException, NSInvalidArgumentException, @"MGL<%- camelize(type) %>Layer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.<%- objCName(property) %> = functionExpression, NSException, NSInvalidArgumentException, @"MGL<%- camelize(type) %>Layer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
 <% } -%>
 <% if (property["transition"] && !property.original) { -%>
diff --git a/platform/darwin/test/MGLSymbolStyleLayerTests.mm b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
index 05e091b5c8..06ff058a8e 100644
--- a/platform/darwin/test/MGLSymbolStyleLayerTests.mm
+++ b/platform/darwin/test/MGLSymbolStyleLayerTests.mm
@@ -63,7 +63,7 @@
                               @"iconAllowsOverlap should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconAllowsOverlap = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -87,8 +87,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconAllowsOverlap = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconAllowsOverlap = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -107,7 +107,7 @@
                               @"iconAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'bottom-right'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::SymbolAnchorType> intervalStops = {{
@@ -145,7 +145,7 @@
                               @"iconIgnoresPlacement should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconIgnoresPlacement = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -169,8 +169,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconIgnoresPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconIgnoresPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -189,7 +189,7 @@
                               @"iconImageName should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Icon Image'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconImageName = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -233,7 +233,7 @@
                               @"iconOffset should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconOffset = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -247,7 +247,7 @@
         XCTAssertEqualObjects(layer.iconOffset, functionExpression,
                               @"iconOffset should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconOffset = functionExpression;
 
         mbgl::style::ExponentialStops<std::array<float, 2>> exponentialStops = { {{18, { 1, 1 }}}, 1.0 };
@@ -258,7 +258,7 @@
         XCTAssertEqualObjects(layer.iconOffset, functionExpression,
                               @"iconOffset should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconOffset = functionExpression;
 
         std::map<float, std::array<float, 2>> innerStops { {18, { 1, 1 }} };
@@ -294,7 +294,7 @@
                               @"iconOptional should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconOptional = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -318,8 +318,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconOptional = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconOptional = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -338,7 +338,7 @@
                               @"iconPadding should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconPadding = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -362,8 +362,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -382,7 +382,7 @@
                               @"iconPitchAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'auto'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconPitchAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::AlignmentType> intervalStops = {{
@@ -406,8 +406,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconPitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconPitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -426,7 +426,7 @@
                               @"iconRotation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconRotation = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -440,7 +440,7 @@
         XCTAssertEqualObjects(layer.iconRotation, functionExpression,
                               @"iconRotation should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconRotation = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -451,7 +451,7 @@
         XCTAssertEqualObjects(layer.iconRotation, functionExpression,
                               @"iconRotation should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconRotation = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -487,7 +487,7 @@
                               @"iconRotationAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'auto'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconRotationAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::AlignmentType> intervalStops = {{
@@ -511,8 +511,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconRotationAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconRotationAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -531,7 +531,7 @@
                               @"iconScale should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconScale = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -545,7 +545,7 @@
         XCTAssertEqualObjects(layer.iconScale, functionExpression,
                               @"iconScale should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconScale = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -556,7 +556,7 @@
         XCTAssertEqualObjects(layer.iconScale, functionExpression,
                               @"iconScale should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconScale = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -592,7 +592,7 @@
                               @"iconTextFit should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'both'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconTextFit = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::IconTextFitType> intervalStops = {{
@@ -616,8 +616,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconTextFit = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconTextFit = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -642,7 +642,7 @@
                               @"iconTextFitPadding should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1, 1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconTextFitPadding = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 4>> intervalStops = {{
@@ -666,8 +666,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconTextFitPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconTextFitPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -686,7 +686,7 @@
                               @"keepsIconUpright should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.keepsIconUpright = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -710,8 +710,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.keepsIconUpright = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.keepsIconUpright = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -730,7 +730,7 @@
                               @"keepsTextUpright should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"false"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.keepsTextUpright = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -754,8 +754,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.keepsTextUpright = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.keepsTextUpright = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -774,7 +774,7 @@
                               @"maximumTextAngle should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.maximumTextAngle = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -798,8 +798,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.maximumTextAngle = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.maximumTextAngle = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -818,7 +818,7 @@
                               @"maximumTextWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.maximumTextWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -832,7 +832,7 @@
         XCTAssertEqualObjects(layer.maximumTextWidth, functionExpression,
                               @"maximumTextWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.maximumTextWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -843,7 +843,7 @@
         XCTAssertEqualObjects(layer.maximumTextWidth, functionExpression,
                               @"maximumTextWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.maximumTextWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -879,7 +879,7 @@
                               @"symbolAvoidsEdges should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.symbolAvoidsEdges = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -903,8 +903,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.symbolAvoidsEdges = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.symbolAvoidsEdges = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -923,7 +923,7 @@
                               @"symbolPlacement should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'line'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.symbolPlacement = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::SymbolPlacementType> intervalStops = {{
@@ -947,8 +947,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.symbolPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.symbolPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -967,7 +967,7 @@
                               @"symbolSpacing should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.symbolSpacing = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -991,8 +991,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.symbolSpacing = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.symbolSpacing = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1011,7 +1011,7 @@
                               @"text should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'Text Field'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.text = functionExpression;
 
         mbgl::style::IntervalStops<std::string> intervalStops = {{
@@ -1049,7 +1049,7 @@
                               @"textAllowsOverlap should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textAllowsOverlap = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -1073,8 +1073,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textAllowsOverlap = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textAllowsOverlap = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1093,7 +1093,7 @@
                               @"textAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'bottom-right'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::SymbolAnchorType> intervalStops = {{
@@ -1131,7 +1131,7 @@
                               @"textFontNames should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{'Text Font', 'Tnof Txet'}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textFontNames = functionExpression;
 
         mbgl::style::IntervalStops<std::vector<std::string>> intervalStops = {{
@@ -1169,7 +1169,7 @@
                               @"textFontSize should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textFontSize = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1183,7 +1183,7 @@
         XCTAssertEqualObjects(layer.textFontSize, functionExpression,
                               @"textFontSize should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textFontSize = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -1194,7 +1194,7 @@
         XCTAssertEqualObjects(layer.textFontSize, functionExpression,
                               @"textFontSize should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textFontSize = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -1230,7 +1230,7 @@
                               @"textIgnoresPlacement should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textIgnoresPlacement = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -1254,8 +1254,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textIgnoresPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textIgnoresPlacement = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1274,7 +1274,7 @@
                               @"textJustification should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'right'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textJustification = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TextJustifyType> intervalStops = {{
@@ -1312,7 +1312,7 @@
                               @"textLetterSpacing should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textLetterSpacing = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1326,7 +1326,7 @@
         XCTAssertEqualObjects(layer.textLetterSpacing, functionExpression,
                               @"textLetterSpacing should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textLetterSpacing = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -1337,7 +1337,7 @@
         XCTAssertEqualObjects(layer.textLetterSpacing, functionExpression,
                               @"textLetterSpacing should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textLetterSpacing = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -1373,7 +1373,7 @@
                               @"textLineHeight should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textLineHeight = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1397,8 +1397,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textLineHeight = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textLineHeight = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1423,7 +1423,7 @@
                               @"textOffset should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textOffset = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -1437,7 +1437,7 @@
         XCTAssertEqualObjects(layer.textOffset, functionExpression,
                               @"textOffset should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textOffset = functionExpression;
 
         mbgl::style::ExponentialStops<std::array<float, 2>> exponentialStops = { {{18, { 1, 1 }}}, 1.0 };
@@ -1448,7 +1448,7 @@
         XCTAssertEqualObjects(layer.textOffset, functionExpression,
                               @"textOffset should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textOffset = functionExpression;
 
         std::map<float, std::array<float, 2>> innerStops { {18, { 1, 1 }} };
@@ -1484,7 +1484,7 @@
                               @"textOptional should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"true"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textOptional = functionExpression;
 
         mbgl::style::IntervalStops<bool> intervalStops = {{
@@ -1508,8 +1508,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textOptional = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textOptional = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1528,7 +1528,7 @@
                               @"textPadding should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textPadding = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1552,8 +1552,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textPadding = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1572,7 +1572,7 @@
                               @"textPitchAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'auto'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textPitchAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::AlignmentType> intervalStops = {{
@@ -1596,8 +1596,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textPitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textPitchAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1616,7 +1616,7 @@
                               @"textRotation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textRotation = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1630,7 +1630,7 @@
         XCTAssertEqualObjects(layer.textRotation, functionExpression,
                               @"textRotation should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textRotation = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -1641,7 +1641,7 @@
         XCTAssertEqualObjects(layer.textRotation, functionExpression,
                               @"textRotation should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textRotation = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -1677,7 +1677,7 @@
                               @"textRotationAlignment should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'auto'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textRotationAlignment = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::AlignmentType> intervalStops = {{
@@ -1701,8 +1701,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textRotationAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textRotationAlignment = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -1721,7 +1721,7 @@
                               @"textTransform should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'lowercase'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textTransform = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TextTransformType> intervalStops = {{
@@ -1759,7 +1759,7 @@
                               @"iconColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -1773,7 +1773,7 @@
         XCTAssertEqualObjects(layer.iconColor, functionExpression,
                               @"iconColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -1784,7 +1784,7 @@
         XCTAssertEqualObjects(layer.iconColor, functionExpression,
                               @"iconColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -1829,7 +1829,7 @@
                               @"iconHaloBlur should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconHaloBlur = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1843,7 +1843,7 @@
         XCTAssertEqualObjects(layer.iconHaloBlur, functionExpression,
                               @"iconHaloBlur should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconHaloBlur = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -1854,7 +1854,7 @@
         XCTAssertEqualObjects(layer.iconHaloBlur, functionExpression,
                               @"iconHaloBlur should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconHaloBlur = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -1899,7 +1899,7 @@
                               @"iconHaloColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconHaloColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -1913,7 +1913,7 @@
         XCTAssertEqualObjects(layer.iconHaloColor, functionExpression,
                               @"iconHaloColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconHaloColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -1924,7 +1924,7 @@
         XCTAssertEqualObjects(layer.iconHaloColor, functionExpression,
                               @"iconHaloColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconHaloColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -1969,7 +1969,7 @@
                               @"iconHaloWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconHaloWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -1983,7 +1983,7 @@
         XCTAssertEqualObjects(layer.iconHaloWidth, functionExpression,
                               @"iconHaloWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconHaloWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -1994,7 +1994,7 @@
         XCTAssertEqualObjects(layer.iconHaloWidth, functionExpression,
                               @"iconHaloWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconHaloWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -2039,7 +2039,7 @@
                               @"iconOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -2053,7 +2053,7 @@
         XCTAssertEqualObjects(layer.iconOpacity, functionExpression,
                               @"iconOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.iconOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -2064,7 +2064,7 @@
         XCTAssertEqualObjects(layer.iconOpacity, functionExpression,
                               @"iconOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.iconOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -2115,7 +2115,7 @@
                               @"iconTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -2139,8 +2139,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -2159,7 +2159,7 @@
                               @"iconTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.iconTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -2183,8 +2183,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.iconTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.iconTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -2203,7 +2203,7 @@
                               @"textColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -2217,7 +2217,7 @@
         XCTAssertEqualObjects(layer.textColor, functionExpression,
                               @"textColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -2228,7 +2228,7 @@
         XCTAssertEqualObjects(layer.textColor, functionExpression,
                               @"textColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -2273,7 +2273,7 @@
                               @"textHaloBlur should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textHaloBlur = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -2287,7 +2287,7 @@
         XCTAssertEqualObjects(layer.textHaloBlur, functionExpression,
                               @"textHaloBlur should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textHaloBlur = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -2298,7 +2298,7 @@
         XCTAssertEqualObjects(layer.textHaloBlur, functionExpression,
                               @"textHaloBlur should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textHaloBlur = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -2343,7 +2343,7 @@
                               @"textHaloColor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"%@", [MGLColor redColor]];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textHaloColor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::Color> intervalStops = {{
@@ -2357,7 +2357,7 @@
         XCTAssertEqualObjects(layer.textHaloColor, functionExpression,
                               @"textHaloColor should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textHaloColor = functionExpression;
 
         mbgl::style::ExponentialStops<mbgl::Color> exponentialStops = { {{18, { 1, 0, 0, 1 }}}, 1.0 };
@@ -2368,7 +2368,7 @@
         XCTAssertEqualObjects(layer.textHaloColor, functionExpression,
                               @"textHaloColor should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textHaloColor = functionExpression;
 
         std::map<float, mbgl::Color> innerStops { {18, { 1, 0, 0, 1 }} };
@@ -2413,7 +2413,7 @@
                               @"textHaloWidth should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textHaloWidth = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -2427,7 +2427,7 @@
         XCTAssertEqualObjects(layer.textHaloWidth, functionExpression,
                               @"textHaloWidth should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textHaloWidth = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -2438,7 +2438,7 @@
         XCTAssertEqualObjects(layer.textHaloWidth, functionExpression,
                               @"textHaloWidth should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textHaloWidth = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -2483,7 +2483,7 @@
                               @"textOpacity should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"0xff"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textOpacity = functionExpression;
 
         mbgl::style::IntervalStops<float> intervalStops = {{
@@ -2497,7 +2497,7 @@
         XCTAssertEqualObjects(layer.textOpacity, functionExpression,
                               @"textOpacity should round-trip camera expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(keyName, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:(keyName, 'linear', nil, %@)", @{@18: constantExpression}];
         layer.textOpacity = functionExpression;
 
         mbgl::style::ExponentialStops<float> exponentialStops = { {{18, 0xff}}, 1.0 };
@@ -2508,7 +2508,7 @@
         XCTAssertEqualObjects(layer.textOpacity, functionExpression,
                               @"textOpacity should round-trip data expressions.");
 
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         layer.textOpacity = functionExpression;
 
         std::map<float, float> innerStops { {18, 0xff} };
@@ -2559,7 +2559,7 @@
                               @"textTranslation should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"{1, 1}"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textTranslation = functionExpression;
 
         mbgl::style::IntervalStops<std::array<float, 2>> intervalStops = {{
@@ -2583,8 +2583,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textTranslation = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 
@@ -2603,7 +2603,7 @@
                               @"textTranslationAnchor should round-trip constant value expressions.");
 
         constantExpression = [NSExpression expressionWithFormat:@"'viewport'"];
-        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
+        NSExpression *functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:($zoomLevel, %@, %@)", constantExpression, @{@18: constantExpression}];
         layer.textTranslationAnchor = functionExpression;
 
         mbgl::style::IntervalStops<mbgl::style::TranslateAnchorType> intervalStops = {{
@@ -2627,8 +2627,8 @@
 
         functionExpression = [NSExpression expressionForKeyPath:@"bogus"];
         XCTAssertThrowsSpecificNamed(layer.textTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION(bogus, 'mgl_stepWithMinimum:stops:', %@, %@)", constantExpression, @{@18: constantExpression}];
-        functionExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{@10: functionExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_step:from:stops:(bogus, %@, %@)", constantExpression, @{@18: constantExpression}];
+        functionExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{@10: functionExpression}];
         XCTAssertThrowsSpecificNamed(layer.textTranslationAnchor = functionExpression, NSException, NSInvalidArgumentException, @"MGLSymbolLayer should raise an exception if a camera-data expression is applied to a property that does not support key paths to feature attributes.");
     }
 }
diff --git a/platform/ios/app/MBXViewController.m b/platform/ios/app/MBXViewController.m
index 5282469223..2a6708a69f 100644
--- a/platform/ios/app/MBXViewController.m
+++ b/platform/ios/app/MBXViewController.m
@@ -969,7 +969,7 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
                                       @12.0f: [UIColor greenColor],
                                       @14.0f: [UIColor blueColor]};
     waterLayer.fillColor = [NSExpression expressionWithFormat:
-                            @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+                            @"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                             waterColorStops];
 
     NSDictionary *fillAntialiasedStops = @{@11: @YES,
@@ -978,7 +978,7 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
                                            @14: @NO,
                                            @15: @YES};
     waterLayer.fillAntialiased = [NSExpression expressionWithFormat:
-                                  @"FUNCTION($zoomLevel, 'mgl_stepWithMinimum:stops:', false, %@)",
+                                  @"mgl_step:from:stops:($zoomLevel, false, %@)",
                                   fillAntialiasedStops];
 }
 
@@ -991,7 +991,7 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
                                      @10: @15,
                                      @15: @30};
     NSExpression *lineWidthExpression = [NSExpression expressionWithFormat:
-                                         @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+                                         @"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                          lineWidthStops];
     roadLayer.lineWidth = lineWidthExpression;
     roadLayer.lineGapWidth = lineWidthExpression;
@@ -1000,7 +1000,7 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
                                          @13: [UIColor yellowColor],
                                          @16: [UIColor cyanColor]};
     roadLayer.lineColor = [NSExpression expressionWithFormat:
-                           @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+                           @"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                            roadLineColorStops];
 
     roadLayer.visible = YES;
@@ -1018,7 +1018,7 @@ typedef NS_ENUM(NSInteger, MBXSettingsMiscellaneousRows) {
     NSDictionary *opacityStops = @{@20.0f: @1.0f,
                                    @5.0f: @0.0f};
     rasterLayer.rasterOpacity = [NSExpression expressionWithFormat:
-                                 @"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+                                 @"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)",
                                  opacityStops];
     [self.mapView.style addLayer:rasterLayer];
 }
diff --git a/platform/ios/docs/guides/For Style Authors.md b/platform/ios/docs/guides/For Style Authors.md
index 1f2803f3ec..122928fd93 100644
--- a/platform/ios/docs/guides/For Style Authors.md
+++ b/platform/ios/docs/guides/For Style Authors.md
@@ -320,8 +320,8 @@ In style specification | Method, function, or predicate type | Format string syn
 `string`               | |
 `to-boolean`           | `boolValue` |
 `to-color`             | |
-`to-number`            | `mgl_numberWithFallbackValues:` |
-`to-string`            | `stringValue` |
+`to-number`            | `mgl_numberWithFallbackValues:` | `CAST(zipCode, 'NSNumber')`
+`to-string`            | `stringValue` | `CAST(ele, 'NSString')`
 `typeof`               | |
 `geometry-type`        | |
 `id`                   | |
@@ -342,11 +342,11 @@ In style specification | Method, function, or predicate type | Format string syn
 `case`                 | `+[NSExpression expressionForConditional:trueExpression:falseExpression:]` | `TERNARY(condition, trueExpression, falseExpression)`
 `coalesce`             | |
 `match`                | |
-`interpolate`          | `mgl_interpolateWithCurveType:parameters:stops:` |
-`step`                 | `mgl_stepWithMinimum:stops:` |
-`let`                  | `mgl_expressionWithContext:` |
+`interpolate`          | `mgl_interpolate:withCurveType:parameters:stops:` |
+`step`                 | `mgl_step:withMinimum:stops:` |
+`let`                  | `mgl_expressionWithContext:` | `MGL_LET('ios', 11, 'macos', 10.13, $ios + $macos)`
 `var`                  | `+[NSExpression expressionForVariable:]` | `$variable`
-`concat`               | `stringByAppendingString:` |
+`concat`               | `mgl_join:` | `mgl_join({'Old', ' ', 'MacDonald'})`
 `downcase`             | `lowercase:` | `lowercase('DOWNTOWN')`
 `upcase`               | `uppercase:` | `uppercase('Elysian Fields')`
 `rgb`                  | `+[UIColor colorWithRed:green:blue:alpha:]` |
diff --git a/platform/ios/docs/guides/Using Style Functions at Runtime.md b/platform/ios/docs/guides/Using Style Functions at Runtime.md
index 0b4e842e0e..7ac8a6aea5 100644
--- a/platform/ios/docs/guides/Using Style Functions at Runtime.md
+++ b/platform/ios/docs/guides/Using Style Functions at Runtime.md
@@ -66,7 +66,7 @@ let stops: [Float: UIColor] = [
 ]
 
 let layer = MGLCircleStyleLayer(identifier: "circles", source: source)
-layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+layer.circleColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)",
                                  stops)
 layer.circleRadius = NSExpression(forConstantValue: 10)
 mapView.style?.insertLayer(layer, below: symbolLayer)
@@ -92,7 +92,7 @@ let stops = [
     18: 18,
 ]
 
-layer.circleRadius = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.5, %@)",
                                   stops)
 ```
 
@@ -111,7 +111,7 @@ let stops: [Float: UIColor] = [
     10: .white,
 ]
 
-layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_stepWithMinimum:stops:', %@, %@)",
+layer.circleColor = NSExpression(format: "mgl_step:from:stops:(mag, %@, %@)",
                                  UIColor.green, stops)
 ```
 
diff --git a/platform/macos/app/MapDocument.m b/platform/macos/app/MapDocument.m
index 23bc652229..4d6c71584b 100644
--- a/platform/macos/app/MapDocument.m
+++ b/platform/macos/app/MapDocument.m
@@ -894,7 +894,7 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
     self.mapView.style.transition = transition;
 
     MGLStyleLayer *waterLayer = [self.mapView.style layerWithIdentifier:@"water"];
-    NSExpression *colorExpression = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{
+    NSExpression *colorExpression = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{
         @0.0: [NSColor redColor],
         @10.0: [NSColor yellowColor],
         @20.0: [NSColor blackColor],
@@ -927,7 +927,7 @@ NS_ARRAY_OF(id <MGLAnnotation>) *MBXFlattenedShapes(NS_ARRAY_OF(id <MGLAnnotatio
         theaterLayer.predicate = [NSPredicate predicateWithFormat:@"maki == 'theatre'"];
         theaterLayer.iconImageName = [NSExpression expressionForConstantValue:NSImageNameIChatTheaterTemplate];
         theaterLayer.iconScale = [NSExpression expressionForConstantValue:@2];
-        theaterLayer.iconColor = [NSExpression expressionWithFormat:@"FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)", @{
+        theaterLayer.iconColor = [NSExpression expressionWithFormat:@"mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'linear', nil, %@)", @{
             @16.0: [NSColor redColor],
             @18.0: [NSColor yellowColor],
             @20.0: [NSColor blackColor],
diff --git a/platform/macos/docs/guides/For Style Authors.md b/platform/macos/docs/guides/For Style Authors.md
index 636cfa7eb7..269f2a8ce1 100644
--- a/platform/macos/docs/guides/For Style Authors.md
+++ b/platform/macos/docs/guides/For Style Authors.md
@@ -313,8 +313,8 @@ In style specification | Method, function, or predicate type | Format string syn
 `string`               | |
 `to-boolean`           | `boolValue` |
 `to-color`             | |
-`to-number`            | `mgl_numberWithFallbackValues:` |
-`to-string`            | `stringValue` |
+`to-number`            | `mgl_numberWithFallbackValues:` | `CAST(zipCode, 'NSNumber')`
+`to-string`            | `stringValue` | `CAST(ele, 'NSString')`
 `typeof`               | |
 `geometry-type`        | |
 `id`                   | |
@@ -335,11 +335,11 @@ In style specification | Method, function, or predicate type | Format string syn
 `case`                 | `+[NSExpression expressionForConditional:trueExpression:falseExpression:]` | `TERNARY(condition, trueExpression, falseExpression)`
 `coalesce`             | |
 `match`                | |
-`interpolate`          | `mgl_interpolateWithCurveType:parameters:stops:` |
-`step`                 | `mgl_stepWithMinimum:stops:` |
-`let`                  | `mgl_expressionWithContext:` |
+`interpolate`          | `mgl_interpolate:withCurveType:parameters:stops:` |
+`step`                 | `mgl_step:withMinimum:stops:` |
+`let`                  | `mgl_expressionWithContext:` | `MGL_LET('ios', 11, 'macos', 10.13, $ios + $macos)`
 `var`                  | `+[NSExpression expressionForVariable:]` | `$variable`
-`concat`               | `stringByAppendingString:` |
+`concat`               | `mgl_join:` | `mgl_join({'Old', ' ', 'MacDonald'})`
 `downcase`             | `lowercase:` | `lowercase('DOWNTOWN')`
 `upcase`               | `uppercase:` | `uppercase('Elysian Fields')`
 `rgb`                  | `+[NSColor colorWithCalibratedRed:green:blue:alpha:]` |
diff --git a/platform/macos/docs/guides/Using Style Functions at Runtime.md b/platform/macos/docs/guides/Using Style Functions at Runtime.md
index 4e854aaaa0..e87cd00185 100644
--- a/platform/macos/docs/guides/Using Style Functions at Runtime.md
+++ b/platform/macos/docs/guides/Using Style Functions at Runtime.md
@@ -66,7 +66,7 @@ let stops: [Float: NSColor] = [
 ]
 
 let layer = MGLCircleStyleLayer(identifier: "circles", source: source)
-layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_interpolateWithCurveType:parameters:stops:', 'linear', nil, %@)",
+layer.circleColor = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:(mag, 'linear', nil, %@)",
                                  stops)
 layer.circleRadius = NSExpression(forConstantValue: 10)
 mapView.style?.insertLayer(layer, below: symbolLayer)
@@ -92,7 +92,7 @@ let stops = [
     18: 18,
 ]
 
-layer.circleRadius = NSExpression(format: "FUNCTION($zoomLevel, 'mgl_interpolateWithCurveType:parameters:stops:', 'exponential', 1.5, %@)",
+layer.circleRadius = NSExpression(format: "mgl_interpolate:withCurveType:parameters:stops:($zoomLevel, 'exponential', 1.5, %@)",
                                   stops)
 ```
 
@@ -111,7 +111,7 @@ let stops: [Float: NSColor] = [
     10: .white,
 ]
 
-layer.circleColor = NSExpression(format: "FUNCTION(mag, 'mgl_stepWithMinimum:stops:', %@, %@)",
+layer.circleColor = NSExpression(format: "mgl_step:from:stops:(mag, %@, %@)",
                                  NSColor.green, stops)
 ```