libstdc++
experimental/numeric
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1 // <experimental/numeric> -*- C++ -*-
2 
3 // Copyright (C) 2015-2024 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 #include <bits/requires_hosted.h> // experimental is currently omitted
40 
41 #if __cplusplus >= 201402L
42 
43 #include <numeric>
44 #include <experimental/type_traits>
45 
46 namespace std _GLIBCXX_VISIBILITY(default)
47 {
48 _GLIBCXX_BEGIN_NAMESPACE_VERSION
49 
50 namespace experimental
51 {
52 inline namespace fundamentals_v2
53 {
54 #define __cpp_lib_experimental_gcd_lcm 201411
55 
56  /// Greatest common divisor
57  template<typename _Mn, typename _Nn>
58  constexpr common_type_t<_Mn, _Nn>
59  gcd(_Mn __m, _Nn __n) noexcept
60  {
61  static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
62  "std::experimental::gcd arguments must be integers");
63  static_assert(_Mn(2) == 2 && _Nn(2) == 2,
64  "std::experimental::gcd arguments must not be bool");
65  namespace __detail = std::__detail;
66  using _Ct = common_type_t<_Mn, _Nn>;
67  const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
68  const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
69  return __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
70  }
71 
72  /// Least common multiple
73  template<typename _Mn, typename _Nn>
74  constexpr common_type_t<_Mn, _Nn>
75  lcm(_Mn __m, _Nn __n)
76  {
77  static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
78  "std::experimental::lcm arguments must be integers");
79  static_assert(_Mn(2) == 2 && _Nn(2) == 2,
80  "std::experimental::lcm arguments must not be bool");
81  namespace __detail = std::__detail;
82  using _Ct = common_type_t<_Mn, _Nn>;
83  const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
84  const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
85  if (__m2 == 0 || __n2 == 0)
86  return 0;
87  _Ct __r = __m2 / __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
88 
89  if _GLIBCXX17_CONSTEXPR (is_signed_v<_Ct>)
90  if (__is_constant_evaluated())
91  return __r * __n2; // constant evaluation can detect overflow here.
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