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* [gcc r11-9113] libstdc++: Add additional overload of std::lerp [PR101870]
@ 2021-10-12 10:59 Jonathan Wakely
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From: Jonathan Wakely @ 2021-10-12 10:59 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:371e12a7fd0295251340eabae77dd060577054c3
commit r11-9113-g371e12a7fd0295251340eabae77dd060577054c3
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu Aug 12 17:35:25 2021 +0100
libstdc++: Add additional overload of std::lerp [PR101870]
The [cmath.syn] p1 wording about additional overloads sufficient to
handle any arithmetic types also applies to std::lerp. This adds a new
overload of std::lerp that does the required promotions to support
arguments of arbitrary arithmetic types.
A new __promoted_t alias template is added, which the C++17 function
templates std::hypot and std::lerp can use to avoid instantiating the
__promote_3 class template.
Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
libstdc++-v3/ChangeLog:
PR libstdc++/101870
* include/c_global/cmath (hypot): Use __promoted_t.
(lerp): Add new overload accepting any arithmetic types.
* include/ext/type_traits.h (__promoted_t): New alias template.
* testsuite/26_numerics/lerp.cc: Moved to...
* testsuite/26_numerics/lerp/1.cc: ...here.
* testsuite/26_numerics/lerp/constexpr.cc: New test.
* testsuite/26_numerics/lerp/version.cc: New test.
(cherry picked from commit 9017326e19fe278d5f62898cca4682b17f8e8e07)
Diff:
---
libstdc++-v3/include/c_global/cmath | 16 ++++++++++++----
libstdc++-v3/include/ext/type_traits.h | 8 +++++++-
.../testsuite/26_numerics/{lerp.cc => lerp/1.cc} | 0
.../testsuite/26_numerics/lerp/constexpr.cc | 21 +++++++++++++++++++++
libstdc++-v3/testsuite/26_numerics/lerp/version.cc | 10 ++++++++++
5 files changed, 50 insertions(+), 5 deletions(-)
diff --git a/libstdc++-v3/include/c_global/cmath b/libstdc++-v3/include/c_global/cmath
index 39a6b036b8c..3233228fdee 100644
--- a/libstdc++-v3/include/c_global/cmath
+++ b/libstdc++-v3/include/c_global/cmath
@@ -1844,7 +1844,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // _GLIBCXX_USE_C99_MATH_TR1
#endif // C++11
-#if __cplusplus > 201402L
+#if __cplusplus >= 201703L
// [c.math.hypot3], three-dimensional hypotenuse
#define __cpp_lib_hypot 201603
@@ -1877,15 +1877,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return std::__hypot3<long double>(__x, __y, __z); }
template<typename _Tp, typename _Up, typename _Vp>
- typename __gnu_cxx::__promote_3<_Tp, _Up, _Vp>::__type
+ __gnu_cxx::__promoted_t<_Tp, _Up, _Vp>
hypot(_Tp __x, _Up __y, _Vp __z)
{
- using __type = typename __gnu_cxx::__promote_3<_Tp, _Up, _Vp>::__type;
+ using __type = __gnu_cxx::__promoted_t<_Tp, _Up, _Vp>;
return std::__hypot3<__type>(__x, __y, __z);
}
#endif // C++17
-#if __cplusplus > 201703L
+#if __cplusplus >= 202002L
// linear interpolation
# define __cpp_lib_interpolate 201902L
@@ -1918,6 +1918,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr long double
lerp(long double __a, long double __b, long double __t) noexcept
{ return std::__lerp(__a, __b, __t); }
+
+ template<typename _Tp, typename _Up, typename _Vp>
+ constexpr __gnu_cxx::__promoted_t<_Tp, _Up, _Vp>
+ lerp(_Tp __x, _Up __y, _Vp __z) noexcept
+ {
+ using __type = __gnu_cxx::__promoted_t<_Tp, _Up, _Vp>;
+ return std::__lerp<__type>(__x, __y, __z);
+ }
#endif // C++20
_GLIBCXX_END_NAMESPACE_VERSION
diff --git a/libstdc++-v3/include/ext/type_traits.h b/libstdc++-v3/include/ext/type_traits.h
index ff067c83f62..065edb4e9a5 100644
--- a/libstdc++-v3/include/ext/type_traits.h
+++ b/libstdc++-v3/include/ext/type_traits.h
@@ -163,7 +163,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ return true; }
#endif
- // For complex and cmath
+ // For arithmetic promotions in <complex> and <cmath>
+
template<typename _Tp, bool = std::__is_integer<_Tp>::__value>
struct __promote
{ typedef double __type; };
@@ -187,6 +188,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
struct __promote<float>
{ typedef float __type; };
+#if __cpp_fold_expressions
+ template<typename... _Tp>
+ using __promoted_t = decltype((typename __promote<_Tp>::__type(0) + ...));
+#endif
+
template<typename _Tp, typename _Up,
typename _Tp2 = typename __promote<_Tp>::__type,
typename _Up2 = typename __promote<_Up>::__type>
diff --git a/libstdc++-v3/testsuite/26_numerics/lerp.cc b/libstdc++-v3/testsuite/26_numerics/lerp/1.cc
similarity index 100%
rename from libstdc++-v3/testsuite/26_numerics/lerp.cc
rename to libstdc++-v3/testsuite/26_numerics/lerp/1.cc
diff --git a/libstdc++-v3/testsuite/26_numerics/lerp/constexpr.cc b/libstdc++-v3/testsuite/26_numerics/lerp/constexpr.cc
new file mode 100644
index 00000000000..f1ab42b5a42
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/lerp/constexpr.cc
@@ -0,0 +1,21 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <cmath>
+
+// Fails template argument deduction unless both arguments are the same type.
+template<typename T>
+constexpr bool
+eq(T result, T expected) { return result == expected; }
+
+static_assert( eq( std::lerp(-10.0, 10.0, 0.25), -5.0 ) );
+static_assert( eq( std::lerp(2.0f, 2.0f, 200.0f), 2.0f ) );
+static_assert( eq( std::lerp(2.0L, 4.0L, 200.0L), 402.0L ) );
+// at least one type is long double, so result is long double
+static_assert( eq( std::lerp(2.0L, 4.0f, -20.0), -38.0L ) );
+// at least one type is double, so result is double:
+static_assert( eq( std::lerp(-8.0f, 10.0, 0.5f), 1.0 ) );
+// int promotes to double, so result is double
+static_assert( eq( std::lerp(0, 1, 0), 0.0 ) );
+// int promotes to double, so result is double
+static_assert( eq( std::lerp(2.0f, -10.0f, 1), -10.0 ) );
diff --git a/libstdc++-v3/testsuite/26_numerics/lerp/version.cc b/libstdc++-v3/testsuite/26_numerics/lerp/version.cc
new file mode 100644
index 00000000000..3ccb032bc67
--- /dev/null
+++ b/libstdc++-v3/testsuite/26_numerics/lerp/version.cc
@@ -0,0 +1,10 @@
+// { dg-options "-std=gnu++2a" }
+// { dg-do preprocess { target c++2a } }
+
+#include <version>
+
+#ifndef __cpp_lib_interpolate
+# error "Feature-test macro for midpoint and lerp missing in <version>"
+#elif __cpp_lib_interpolate != 201902L
+# error "Feature-test macro for midpoint and lerp has wrong value in <version>"
+#endif
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