Add AZStd::lerp math function, based on C++20 (#3468)

* Add AZStd::lerp math function, based on c++20 Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Add unit test for AZStd::lerp, based on libc++ ones Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * written a reduced set of lerp tests, but now the license is correct Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Update Code/Framework/AzCore/AzCore/std/math.h Co-authored-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com> Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Update Code/Framework/AzCore/Tests/AZStd/Math.cpp Co-authored-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com> Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * fix the github suggestion merge Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Copy some AZ::Lerp tests to std::lerp test suite + clang-format Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Cleanup lerp test cases Remove comments that suggested very heavy tests that required things like `for every t1..` Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Fix unit test compilation issues Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * fix whitespace issue Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Use `TypeParam` in TYPED_TEST Co-authored-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com> Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * Remove unneeded new-lines Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> * remove unused infinity Signed-off-by: nemerle <96597+nemerle@users.noreply.github.com> Co-authored-by: lumberyard-employee-dm <56135373+lumberyard-employee-dm@users.noreply.github.com>
2021-10-11 12:55:24 +02:00
parent 7b1dd01d1d
commit b91d503a82
3 changed files with 92 additions and 0 deletions
@@ -30,4 +30,49 @@ namespace AZStd
    using std::sqrt;
    using std::tan;
    using std::trunc;
+
+} // namespace AZStd
+
+// from c++20 standard
+namespace AZStd::Internal
+{
+    template<typename T>
+    constexpr T lerp(T a, T b, T t) noexcept
+    {
+        if ((a <= 0 && b >= 0) || (a >= 0 && b <= 0))
+        {
+            return t * b + (1 - t) * a;
+        }
+        if (t == 1)
+        {
+            return b;
+        }
+        const T x = a + t * (b - a);
+        if ((t > 1) == (b > a))
+        {
+            return b < x ? x : b;
+        }
+        else
+        {
+            return x < b ? x : b;
+        }
+    }
+} // namespace AZStd::Internal
+
+namespace AZStd
+{
+    constexpr float lerp(float a, float b, float t) noexcept
+    {
+        return Internal::lerp(a, b, t);
+    }
+
+    constexpr double lerp(double a, double b, double t) noexcept
+    {
+        return Internal::lerp(a, b, t);
+    }
+
+    constexpr long double lerp(long double a, long double b, long double t) noexcept
+    {
+        return Internal::lerp(a, b, t);
+    }
 } // namespace AZStd
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) Contributors to the Open 3D Engine Project.
+ * For complete copyright and license terms please see the LICENSE at the root of this distribution.
+ *
+ * SPDX-License-Identifier: Apache-2.0 OR MIT
+ *
+ */
+
+#include <AzCore/UnitTest/TestTypes.h>
+#include <AzCore/std/math.h>
+
+namespace UnitTest
+{
+    template<typename T>
+    class StdMathTest : public ::testing::Test
+    {
+    };
+
+    using MathTestConfigs = ::testing::Types<float, double, long double>;
+    TYPED_TEST_CASE(StdMathTest, MathTestConfigs);
+
+    TYPED_TEST(StdMathTest, LerpOperations)
+    {
+        using AZStd::lerp;
+        using ::testing::Eq;
+        using T = TypeParam;
+
+        constexpr T maxNumber = AZStd::numeric_limits<T>::max();
+        constexpr T eps = AZStd::numeric_limits<T>::epsilon();
+        constexpr T a{ 42 };
+
+        // exactness: lerp(a,b,0)==a && lerp(a,b,1)==b
+        EXPECT_THAT(lerp(eps, maxNumber, T(0)), Eq(eps));
+        EXPECT_THAT(lerp(eps, maxNumber, T(1)), Eq(maxNumber));
+
+        // consistency: lerp(a,a,t)==a
+        EXPECT_THAT(lerp(a, a, T(0.5)), Eq(a));
+        EXPECT_THAT(lerp(eps, eps, T(0.5)), Eq(eps));
+
+        // a few generic tests taken from MathUtilTests.cpp
+        EXPECT_EQ(T(2.5), lerp(T(2), T(4), T(0.25)));
+        EXPECT_EQ(T(6.0), lerp(T(2), T(4), T(2.0)));
+        EXPECT_EQ(T(3.5), lerp(T(2), T(4), T(0.75)));
+        EXPECT_EQ(T(0.0), lerp(T(2), T(4), T(-1.0)));
+    }
+} // namespace UnitTest
@@ -195,6 +195,7 @@ set(FILES
    AZStd/LockFreeQueues.cpp
    AZStd/LockFreeStacks.cpp
    AZStd/LockTests.cpp
+    AZStd/Math.cpp
    AZStd/Numeric.cpp
    AZStd/Ordered.cpp
    AZStd/Optional.cpp