libstdc++
experimental/numeric
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1 // <experimental/numeric> -*- C++ -*-
2 
3 // Copyright (C) 2015-2025 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 #ifdef _GLIBCXX_SYSHDR
38 #pragma GCC system_header
39 #endif
40 
41 #include <bits/requires_hosted.h> // experimental is currently omitted
42 
43 #if __cplusplus >= 201402L
44 
45 #include <numeric>
46 #include <experimental/type_traits>
47 
48 namespace std _GLIBCXX_VISIBILITY(default)
49 {
50 _GLIBCXX_BEGIN_NAMESPACE_VERSION
51 
52 namespace experimental
53 {
54 inline namespace fundamentals_v2
55 {
56 #define __cpp_lib_experimental_gcd_lcm 201411
57 
58  /// Greatest common divisor
59  template<typename _Mn, typename _Nn>
60  constexpr common_type_t<_Mn, _Nn>
61  gcd(_Mn __m, _Nn __n) noexcept
62  {
63  static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
64  "std::experimental::gcd arguments must be integers");
65  static_assert(_Mn(2) == 2 && _Nn(2) == 2,
66  "std::experimental::gcd arguments must not be bool");
67  namespace __detail = std::__detail;
68  using _Ct = common_type_t<_Mn, _Nn>;
69  const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
70  const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
71  return __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
72  }
73 
74  /// Least common multiple
75  template<typename _Mn, typename _Nn>
76  constexpr common_type_t<_Mn, _Nn>
77  lcm(_Mn __m, _Nn __n)
78  {
79  static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
80  "std::experimental::lcm arguments must be integers");
81  static_assert(_Mn(2) == 2 && _Nn(2) == 2,
82  "std::experimental::lcm arguments must not be bool");
83  namespace __detail = std::__detail;
84  using _Ct = common_type_t<_Mn, _Nn>;
85  const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
86  const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
87  if (__m2 == 0 || __n2 == 0)
88  return 0;
89  _Ct __r = __m2 / __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
90 
91  if _GLIBCXX17_CONSTEXPR (is_signed_v<_Ct>)
92  if (__is_constant_evaluated())
93  return __r * __n2; // constant evaluation can detect overflow here.
94 
95  bool __overflow = __builtin_mul_overflow(__r, __n2, &__r);
96  __glibcxx_assert(!__overflow);
97  return __r;
98  }
99 } // namespace fundamentals_v2
100 } // namespace experimental
101 
102 _GLIBCXX_END_NAMESPACE_VERSION
103 } // namespace std
104 
105 #endif // __cplusplus <= 201103L
106 
107 #endif // _GLIBCXX_EXPERIMENTAL_NUMERIC