Implement 'lerp'; which is the last bit of P0811. Mark that paper as complete.

llvm-svn: 359211

1 files changed, 75 insertions, 0 deletions

diff --git a/libcxx/test/std/numerics/c.math/c.math.lerp/c.math.lerp.pass.cpp b/libcxx/test/std/numerics/c.math/c.math.lerp/c.math.lerp.pass.cpp
new file mode 100644
index 00000000000..2ab41c18225
--- /dev/null
+++ b/libcxx/test/std/numerics/c.math/c.math.lerp/c.math.lerp.pass.cpp
@@ -0,0 +1,75 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+// <cmath>
+
+// constexpr float lerp(float a, float b, float t);
+// constexpr double lerp(double a, double b, double t);
+// constexpr long double lerp(long double a, long double b, long double t);
+
+
+#include <cmath>
+#include <limits>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+#include "fp_compare.h"
+
+template <typename T>
+constexpr bool constexpr_test()
+{
+    return std::lerp(T( 0), T(12), T(0))   == T(0)
+        && std::lerp(T(12), T( 0), T(0.5)) == T(6)
+        && std::lerp(T( 0), T(12), T(2))   == T(24);
+}
+
+
+template <typename T>
+void test()
+{
+    ASSERT_SAME_TYPE(T, decltype(std::lerp(T(), T(), T())));
+    LIBCPP_ASSERT_NOEXCEPT(      std::lerp(T(), T(), T()));
+
+//     constexpr T minV = std::numeric_limits<T>::min();
+    constexpr T maxV = std::numeric_limits<T>::max();
+    constexpr T inf  = std::numeric_limits<T>::infinity();
+
+//  Things that can be compared exactly
+    assert((std::lerp(T( 0), T(12), T(0)) == T(0)));
+    assert((std::lerp(T( 0), T(12), T(1)) == T(12)));
+    assert((std::lerp(T(12), T( 0), T(0)) == T(12)));
+    assert((std::lerp(T(12), T( 0), T(1)) == T(0)));
+    
+    assert((std::lerp(T( 0), T(12), T(0.5)) == T(6)));
+    assert((std::lerp(T(12), T( 0), T(0.5)) == T(6)));
+    assert((std::lerp(T( 0), T(12), T(2))   == T(24)));
+    assert((std::lerp(T(12), T( 0), T(2))   == T(-12)));
+
+    assert((std::lerp(maxV, maxV/10, T(0)) == maxV));
+    assert((std::lerp(maxV/10, maxV, T(1)) == maxV));
+
+    assert((std::lerp(T(2.3), T(2.3), inf) == T(2.3)));
+
+    assert(std::lerp(T( 0), T( 0), T(23)) ==  T(0));
+    assert(std::isnan(std::lerp(T( 0), T( 0), inf)));
+}
+
+
+int main(int, char**)
+{
+    static_assert(constexpr_test<float>(), "");
+    static_assert(constexpr_test<double>(), "");
+    static_assert(constexpr_test<long double>(), "");
+    
+    test<float>();
+    test<double>();
+    test<long double>();
+    
+    return 0;
+}