[ios, macos] Add tangent NSExpresssion operator.

2 files changed, 17 insertions, 0 deletions

diff --git a/platform/darwin/src/NSExpression+MGLAdditions.mm b/platform/darwin/src/NSExpression+MGLAdditions.mm
index 8c79fd43f8..e641c79628 100644
--- a/platform/darwin/src/NSExpression+MGLAdditions.mm
+++ b/platform/darwin/src/NSExpression+MGLAdditions.mm
@@ -73,6 +73,7 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
     INSTALL_METHOD(mgl_asin:);
     INSTALL_METHOD(mgl_sin:);
     INSTALL_METHOD(mgl_atan:);
+    INSTALL_METHOD(mgl_tan:);
     
     // Install functions that resemble control structures, taking arbitrary
     // numbers of arguments. Vararg aftermarket functions need to be declared
@@ -138,6 +139,13 @@ const MGLExpressionInterpolationMode MGLExpressionInterpolationModeCubicBezier =
 }
 
 /**
+ Computes the principal value of the tangent.
+ */
+- (NSNumber *)mgl_tan:(NSNumber *)number {
+    return @(tan(number.doubleValue));
+}
+
+/**
  A placeholder for a method that evaluates an interpolation expression.
  */
 - (id)mgl_interpolate:(id)inputExpression withCurveType:(NSString *)curveType parameters:(NSDictionary *)params stops:(NSDictionary *)stops {
@@ -720,6 +728,7 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             @"asin" : @"mgl_asin:",
             @"sin" : @"mgl_sin:",
             @"atan" : @"mgl_atan:",
+            @"tan" : @"mgl_tan:",
             @"floor": @"floor:",
             @"ceil": @"ceiling:",
             @"^": @"raise:toPower:",
@@ -967,6 +976,7 @@ NSArray *MGLSubexpressionsWithJSONObjects(NSArray *objects) {
             @"mgl_asin:" : @"asin",
             @"mgl_sin:" : @"sin",
             @"mgl_atan:" : @"atan",
+            @"mgl_tan:" : @"tan",
             // Vararg aftermarket expressions need to be declared with an explicit and implicit first argument.
             @"MGL_LET": @"let",
             @"MGL_LET:": @"let",
diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index 4e18ad694d..864310356c 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -567,6 +567,13 @@ using namespace std::string_literals;
         XCTAssertEqualWithAccuracy(value.doubleValue, 1.52, 0.001);
         XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
     }
+    {
+        NSExpression *expression = [NSExpression expressionForFunction:@"mgl_tan:" arguments:@[MGLConstantExpression(@0)]];
+        NSArray *jsonExpression = @[@"tan", @0];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([expression expressionValueWithObject:nil context:nil], @0);
+        XCTAssertEqualObjects([NSExpression expressionWithMGLJSONObject:jsonExpression], expression);
+    }
 }
 
 - (void)testStringFormattingExpressionObject {