From 606dda21c8bcd4c2574e5b28f8125f01e38955c6 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Mon, 3 Oct 2016 18:01:10 +0100
Subject: Define std::gcd and std::lcm for C++17

	* doc/xml/manual/status_cxx2017.xml: Update gcd/lcm status.
	* doc/html/*: Regenerate.
	* include/experimental/numeric (__abs): Move to <numeric>.
	(gcd, lcm): Use __detail::gcd and __detail::lcm.
	* include/std/numeric (__detail::__abs_integral)
	(__detail::__gcd, __detail::__lcm): Define.
	(gcd, lcm): Define for C++17.
	* testsuite/26_numerics/gcd/1.cc: New test.
	* testsuite/26_numerics/lcm/1.cc: New test.
	* testsuite/experimental/numeric/gcd.cc: Swap contents with ...
	* testsuite/experimental/numeric/lcd.cc: ... this.

From-SVN: r240723
---
 libstdc++-v3/include/std/numeric | 79 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

(limited to 'libstdc++-v3/include/std/numeric')

diff --git a/libstdc++-v3/include/std/numeric b/libstdc++-v3/include/std/numeric
index 47a7cb8..7b1ab98 100644
--- a/libstdc++-v3/include/std/numeric
+++ b/libstdc++-v3/include/std/numeric
@@ -74,4 +74,83 @@
  * math functions.
  */
 
+#if __cplusplus >= 201402L
+#include <type_traits>
+
+namespace std _GLIBCXX_VISIBILITY(default)
+{
+namespace __detail
+{
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+  // std::abs is not constexpr and doesn't support unsigned integers.
+  template<typename _Tp>
+    constexpr
+    enable_if_t<__and_<is_integral<_Tp>, is_signed<_Tp>>::value, _Tp>
+    __abs_integral(_Tp __val)
+    { return __val < 0 ? -__val : __val; }
+
+  template<typename _Tp>
+    constexpr
+    enable_if_t<__and_<is_integral<_Tp>, is_unsigned<_Tp>>::value, _Tp>
+    __abs_integral(_Tp __val)
+    { return __val; }
+
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    __gcd(_Mn __m, _Nn __n)
+    {
+      return __m == 0 ? __detail::__abs_integral(__n)
+	: __n == 0 ? __detail::__abs_integral(__m)
+	: __detail::__gcd(__n, __m % __n);
+    }
+
+  /// Least common multiple
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    __lcm(_Mn __m, _Nn __n)
+    {
+      return (__m != 0 && __n != 0)
+	? (__detail::__abs_integral(__m) / __detail::__gcd(__m, __n))
+	  * __detail::__abs_integral(__n)
+	: 0;
+    }
+
+_GLIBCXX_END_NAMESPACE_VERSION
+}
+
+_GLIBCXX_BEGIN_NAMESPACE_VERSION
+
+#if __cplusplus > 201402L
+
+#define __cpp_lib_gcd 201606
+  /// Greatest common divisor
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    gcd(_Mn __m, _Nn __n)
+    {
+      static_assert(is_integral<_Mn>::value, "arguments to gcd are integers");
+      static_assert(is_integral<_Nn>::value, "arguments to gcd are integers");
+      return __detail::__gcd(__m, __n);
+    }
+
+#define __cpp_lib_lcm 201606
+  /// Least common multiple
+  template<typename _Mn, typename _Nn>
+    constexpr common_type_t<_Mn, _Nn>
+    lcm(_Mn __m, _Nn __n)
+    {
+      static_assert(is_integral<_Mn>::value, "arguments to lcm are integers");
+      static_assert(is_integral<_Nn>::value, "arguments to lcm are integers");
+      return __detail::__lcm(__m, __n);
+    }
+
+#endif // C++17
+
+_GLIBCXX_END_NAMESPACE_VERSION
+} // namespace std
+
+#endif // C++14
+
+
 #endif /* _GLIBCXX_NUMERIC */
-- 
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