libstdc++
experimental/numeric
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1// <experimental/numeric> -*- C++ -*-
2
3// Copyright (C) 2015-2021 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file experimental/numeric
26 * This is a TS C++ Library header.
27 * @ingroup libfund-ts
28 */
29
30//
31// N4336 Working Draft, C++ Extensions for Library Fundamentals, Version 2
32//
33
34#ifndef _GLIBCXX_EXPERIMENTAL_NUMERIC
35#define _GLIBCXX_EXPERIMENTAL_NUMERIC 1
36
37#pragma GCC system_header
38
39#if __cplusplus >= 201402L
40
41#include <numeric>
42#include <experimental/type_traits>
43
44namespace std _GLIBCXX_VISIBILITY(default)
45{
46_GLIBCXX_BEGIN_NAMESPACE_VERSION
47
48namespace experimental
49{
50inline namespace fundamentals_v2
51{
52#define __cpp_lib_experimental_gcd_lcm 201411
53
54 /// Greatest common divisor
55 template<typename _Mn, typename _Nn>
56 constexpr common_type_t<_Mn, _Nn>
57 gcd(_Mn __m, _Nn __n) noexcept
58 {
59 static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
60 "std::experimental::gcd arguments must be integers");
61 static_assert(_Mn(2) == 2 && _Nn(2) == 2,
62 "std::experimental::gcd arguments must not be bool");
63 namespace __detail = std::__detail;
64 using _Ct = common_type_t<_Mn, _Nn>;
65 const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
66 const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
67 return __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
68 }
69
70 /// Least common multiple
71 template<typename _Mn, typename _Nn>
72 constexpr common_type_t<_Mn, _Nn>
73 lcm(_Mn __m, _Nn __n)
74 {
75 static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
76 "std::experimental::lcm arguments must be integers");
77 static_assert(_Mn(2) == 2 && _Nn(2) == 2,
78 "std::experimental::lcm arguments must not be bool");
79 namespace __detail = std::__detail;
80 using _Ct = common_type_t<_Mn, _Nn>;
81 const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
82 const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
83 if (__m2 == 0 || __n2 == 0)
84 return 0;
85 _Ct __r = __m2 / __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
86
87#if defined _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
88 if _GLIBCXX17_CONSTEXPR (is_signed_v<_Ct>)
89 if (__builtin_is_constant_evaluated())
90 return __r * __n2; // constant evaluation can detect overflow here.
91#endif
92
93 bool __overflow = __builtin_mul_overflow(__r, __n2, &__r);
94 __glibcxx_assert(!__overflow);
95 return __r;
96 }
97} // namespace fundamentals_v2
98} // namespace experimental
99
100_GLIBCXX_END_NAMESPACE_VERSION
101} // namespace std
102
103#endif // __cplusplus <= 201103L
104
105#endif // _GLIBCXX_EXPERIMENTAL_NUMERIC