[core] Extract Function::evaluation to a separate class (#4811)

This allows the Function<Faded<T>> partial specialization to be eliminated, giving all property functions a consistent storage type.

1 files changed, 41 insertions, 37 deletions

diff --git a/test/style/functions.cpp b/test/style/functions.cpp
index 26b952d7b4..2389459dbc 100644
--- a/test/style/functions.cpp
+++ b/test/style/functions.cpp
@@ -2,58 +2,62 @@
 #include <mbgl/test/util.hpp>
 
 #include <mbgl/style/function.hpp>
+#include <mbgl/style/function_evaluator.hpp>
 #include <mbgl/style/style_calculation_parameters.hpp>
 
 using namespace mbgl;
 
 TEST(Function, Constant) {
-    EXPECT_EQ(2.0f, mbgl::Function<float>(2).evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(3.8f, mbgl::Function<float>(3.8).evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(22.0f, mbgl::Function<float>(22).evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(2.0f, mbgl::Function<float>(2).evaluate(StyleCalculationParameters(4)));
-    EXPECT_EQ(3.8f, mbgl::Function<float>(3.8).evaluate(StyleCalculationParameters(4)));
-    EXPECT_EQ(22.0f, mbgl::Function<float>(22).evaluate(StyleCalculationParameters(4)));
-    EXPECT_EQ(2.0f, mbgl::Function<float>(2).evaluate(StyleCalculationParameters(22)));
-    EXPECT_EQ(3.8f, mbgl::Function<float>(3.8).evaluate(StyleCalculationParameters(22)));
-    EXPECT_EQ(22.0f, mbgl::Function<float>(22).evaluate(StyleCalculationParameters(22)));
+    NormalFunctionEvaluator<float> evaluate;
+    EXPECT_EQ(2.0f, evaluate(Function<float>(2), StyleCalculationParameters(0)));
+    EXPECT_EQ(3.8f, evaluate(Function<float>(3.8), StyleCalculationParameters(0)));
+    EXPECT_EQ(22.0f, evaluate(Function<float>(22), StyleCalculationParameters(0)));
+    EXPECT_EQ(2.0f, evaluate(Function<float>(2), StyleCalculationParameters(4)));
+    EXPECT_EQ(3.8f, evaluate(Function<float>(3.8), StyleCalculationParameters(4)));
+    EXPECT_EQ(22.0f, evaluate(Function<float>(22), StyleCalculationParameters(4)));
+    EXPECT_EQ(2.0f, evaluate(Function<float>(2), StyleCalculationParameters(22)));
+    EXPECT_EQ(3.8f, evaluate(Function<float>(3.8), StyleCalculationParameters(22)));
+    EXPECT_EQ(22.0f, evaluate(Function<float>(22), StyleCalculationParameters(22)));
 }
 
 TEST(Function, Stops) {
+    NormalFunctionEvaluator<float> evaluate;
+
     // Explicit constant slope in fringe regions.
-    mbgl::Function<float> slope_1({ { 0, 1.5 }, { 6, 1.5 }, { 8, 3 }, { 22, 3 } }, 1.75);
-    EXPECT_EQ(1.5, slope_1.evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(1.5, slope_1.evaluate(StyleCalculationParameters(4)));
-    EXPECT_EQ(1.5, slope_1.evaluate(StyleCalculationParameters(6)));
-    ASSERT_FLOAT_EQ(2.0454545454545454, slope_1.evaluate(StyleCalculationParameters(7)));
-    EXPECT_EQ(3.0, slope_1.evaluate(StyleCalculationParameters(8)));
-    EXPECT_EQ(3.0, slope_1.evaluate(StyleCalculationParameters(9)));
-    EXPECT_EQ(3.0, slope_1.evaluate(StyleCalculationParameters(15)));
-    EXPECT_EQ(3.0, slope_1.evaluate(StyleCalculationParameters(22)));
+    Function<float> slope_1({ { 0, 1.5 }, { 6, 1.5 }, { 8, 3 }, { 22, 3 } }, 1.75);
+    EXPECT_EQ(1.5, evaluate(slope_1, StyleCalculationParameters(0)));
+    EXPECT_EQ(1.5, evaluate(slope_1, StyleCalculationParameters(4)));
+    EXPECT_EQ(1.5, evaluate(slope_1, StyleCalculationParameters(6)));
+    ASSERT_FLOAT_EQ(2.0454545454545454, evaluate(slope_1, StyleCalculationParameters(7)));
+    EXPECT_EQ(3.0, evaluate(slope_1, StyleCalculationParameters(8)));
+    EXPECT_EQ(3.0, evaluate(slope_1, StyleCalculationParameters(9)));
+    EXPECT_EQ(3.0, evaluate(slope_1, StyleCalculationParameters(15)));
+    EXPECT_EQ(3.0, evaluate(slope_1, StyleCalculationParameters(22)));
 
 
     // Test constant values in fringe regions.
-    mbgl::Function<float> slope_2({ { 6, 1.5 }, { 8, 3 } }, 1.75);
-    EXPECT_EQ(1.5, slope_2.evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(1.5, slope_2.evaluate(StyleCalculationParameters(4)));
-    EXPECT_EQ(1.5, slope_2.evaluate(StyleCalculationParameters(6)));
-    ASSERT_FLOAT_EQ(2.0454545454545454, slope_2.evaluate(StyleCalculationParameters(7)));
-    EXPECT_EQ(3.0, slope_2.evaluate(StyleCalculationParameters(8)));
-    EXPECT_EQ(3.0, slope_2.evaluate(StyleCalculationParameters(9)));
-    EXPECT_EQ(3.0, slope_2.evaluate(StyleCalculationParameters(15)));
-    EXPECT_EQ(3.0, slope_2.evaluate(StyleCalculationParameters(22)));
+    Function<float> slope_2({ { 6, 1.5 }, { 8, 3 } }, 1.75);
+    EXPECT_EQ(1.5, evaluate(slope_2, StyleCalculationParameters(0)));
+    EXPECT_EQ(1.5, evaluate(slope_2, StyleCalculationParameters(4)));
+    EXPECT_EQ(1.5, evaluate(slope_2, StyleCalculationParameters(6)));
+    ASSERT_FLOAT_EQ(2.0454545454545454, evaluate(slope_2, StyleCalculationParameters(7)));
+    EXPECT_EQ(3.0, evaluate(slope_2, StyleCalculationParameters(8)));
+    EXPECT_EQ(3.0, evaluate(slope_2, StyleCalculationParameters(9)));
+    EXPECT_EQ(3.0, evaluate(slope_2, StyleCalculationParameters(15)));
+    EXPECT_EQ(3.0, evaluate(slope_2, StyleCalculationParameters(22)));
 
     // Test no values.
-    mbgl::Function<float> slope_3({}, 1.75);
-    EXPECT_EQ(1, slope_3.evaluate(StyleCalculationParameters(2)));
-    EXPECT_EQ(1, slope_3.evaluate(StyleCalculationParameters(6)));
-    EXPECT_EQ(1, slope_3.evaluate(StyleCalculationParameters(12)));
+    Function<float> slope_3({}, 1.75);
+    EXPECT_EQ(1, evaluate(slope_3, StyleCalculationParameters(2)));
+    EXPECT_EQ(1, evaluate(slope_3, StyleCalculationParameters(6)));
+    EXPECT_EQ(1, evaluate(slope_3, StyleCalculationParameters(12)));
 
 
     // Explicit constant slope in fringe regions.
-    mbgl::Function<float> slope_4({ { 0, 2 }, { 8, 10 } }, 1);
-    EXPECT_EQ(2, slope_4.evaluate(StyleCalculationParameters(0)));
-    EXPECT_EQ(3, slope_4.evaluate(StyleCalculationParameters(1)));
-    EXPECT_EQ(4, slope_4.evaluate(StyleCalculationParameters(2)));
-    EXPECT_EQ(4.75, slope_4.evaluate(StyleCalculationParameters(2.75)));
-    EXPECT_EQ(10, slope_4.evaluate(StyleCalculationParameters(8)));
+    Function<float> slope_4({ { 0, 2 }, { 8, 10 } }, 1);
+    EXPECT_EQ(2, evaluate(slope_4, StyleCalculationParameters(0)));
+    EXPECT_EQ(3, evaluate(slope_4, StyleCalculationParameters(1)));
+    EXPECT_EQ(4, evaluate(slope_4, StyleCalculationParameters(2)));
+    EXPECT_EQ(4.75, evaluate(slope_4, StyleCalculationParameters(2.75)));
+    EXPECT_EQ(10, evaluate(slope_4, StyleCalculationParameters(8)));
 }