libstdc++-v3/include/experimental/numeric

// <experimental/numeric> -*- C++ -*-

// Copyright (C) 2015-2026 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <http://www.gnu.org/licenses/>.

/** @file experimental/numeric
 *  This is a TS C++ Library header.
 *  @ingroup libfund-ts
 */

//
// N4336 Working Draft, C++ Extensions for Library Fundamentals, Version 2
//

#ifndef _GLIBCXX_EXPERIMENTAL_NUMERIC
#define _GLIBCXX_EXPERIMENTAL_NUMERIC 1

#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif

#include <bits/requires_hosted.h> // experimental is currently omitted

#if __cplusplus >= 201402L

#include <numeric>
#include <experimental/type_traits>

namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

namespace experimental
{
inline namespace fundamentals_v2
{
#define __cpp_lib_experimental_gcd_lcm 201411

  /// Greatest common divisor
  template<typename _Mn, typename _Nn>
    constexpr common_type_t<_Mn, _Nn>
    gcd(_Mn __m, _Nn __n) noexcept
    {
      static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
		    "std::experimental::gcd arguments must be integers");
      static_assert(_Mn(2) == 2 && _Nn(2) == 2,
		    "std::experimental::gcd arguments must not be bool");
      namespace __detail = std::__detail;
      using _Ct = common_type_t<_Mn, _Nn>;
      const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
      const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
      return __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);
    }

  /// Least common multiple
  template<typename _Mn, typename _Nn>
    constexpr common_type_t<_Mn, _Nn>
    lcm(_Mn __m, _Nn __n)
    {
      static_assert(is_integral_v<_Mn> && is_integral_v<_Nn>,
	  "std::experimental::lcm arguments must be integers");
      static_assert(_Mn(2) == 2 && _Nn(2) == 2,
	  "std::experimental::lcm arguments must not be bool");
      namespace __detail = std::__detail;
      using _Ct = common_type_t<_Mn, _Nn>;
      const _Ct __m2 = __detail::__abs_r<_Ct>(__m);
      const _Ct __n2 = __detail::__abs_r<_Ct>(__n);
      if (__m2 == 0 || __n2 == 0)
	return 0;
      _Ct __r = __m2 / __detail::__gcd<make_unsigned_t<_Ct>>(__m2, __n2);

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wc++17-extensions" // if constexpr
      if constexpr (is_signed_v<_Ct>)
	if (__is_constant_evaluated())
	  return __r * __n2; // constant evaluation can detect overflow here.
#pragma GCC diagnostic pop

      bool __overflow = __builtin_mul_overflow(__r, __n2, &__r);
      __glibcxx_assert(!__overflow);
      return __r;
    }
} // namespace fundamentals_v2
} // namespace experimental

_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std

#endif // __cplusplus <= 201103L

#endif // _GLIBCXX_EXPERIMENTAL_NUMERIC