1 // -*- C++ -*- 2 //===----------------------------------------------------------------------===// 3 // 4 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 5 // See https://llvm.org/LICENSE.txt for license information. 6 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef _LIBCPP___NUMERIC_GCD_LCM_H 11 #define _LIBCPP___NUMERIC_GCD_LCM_H 12 13 #include <__assert> 14 #include <__config> 15 #include <__type_traits/common_type.h> 16 #include <__type_traits/is_integral.h> 17 #include <__type_traits/is_same.h> 18 #include <__type_traits/is_signed.h> 19 #include <__type_traits/make_unsigned.h> 20 #include <limits> 21 22 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 23 # pragma GCC system_header 24 #endif 25 26 _LIBCPP_PUSH_MACROS 27 #include <__undef_macros> 28 29 _LIBCPP_BEGIN_NAMESPACE_STD 30 31 #if _LIBCPP_STD_VER >= 17 32 33 template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> 34 struct __ct_abs; 35 36 template <typename _Result, typename _Source> 37 struct __ct_abs<_Result, _Source, true> { 38 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI _Result operator()(_Source __t) const noexcept { 39 if (__t >= 0) 40 return __t; 41 if (__t == numeric_limits<_Source>::min()) 42 return -static_cast<_Result>(__t); 43 return -__t; 44 } 45 }; 46 47 template <typename _Result, typename _Source> 48 struct __ct_abs<_Result, _Source, false> { 49 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI _Result operator()(_Source __t) const noexcept { return __t; } 50 }; 51 52 template <class _Tp> 53 _LIBCPP_CONSTEXPR _LIBCPP_HIDDEN _Tp __gcd(_Tp __m, _Tp __n) { 54 static_assert((!is_signed<_Tp>::value), ""); 55 return __n == 0 ? __m : std::__gcd<_Tp>(__n, __m % __n); 56 } 57 58 template <class _Tp, class _Up> 59 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI common_type_t<_Tp, _Up> gcd(_Tp __m, _Up __n) { 60 static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types"); 61 static_assert((!is_same<__remove_cv_t<_Tp>, bool>::value), "First argument to gcd cannot be bool"); 62 static_assert((!is_same<__remove_cv_t<_Up>, bool>::value), "Second argument to gcd cannot be bool"); 63 using _Rp = common_type_t<_Tp, _Up>; 64 using _Wp = make_unsigned_t<_Rp>; 65 return static_cast<_Rp>( 66 std::__gcd(static_cast<_Wp>(__ct_abs<_Rp, _Tp>()(__m)), static_cast<_Wp>(__ct_abs<_Rp, _Up>()(__n)))); 67 } 68 69 template <class _Tp, class _Up> 70 _LIBCPP_CONSTEXPR _LIBCPP_HIDE_FROM_ABI common_type_t<_Tp, _Up> lcm(_Tp __m, _Up __n) { 71 static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types"); 72 static_assert((!is_same<__remove_cv_t<_Tp>, bool>::value), "First argument to lcm cannot be bool"); 73 static_assert((!is_same<__remove_cv_t<_Up>, bool>::value), "Second argument to lcm cannot be bool"); 74 if (__m == 0 || __n == 0) 75 return 0; 76 77 using _Rp = common_type_t<_Tp, _Up>; 78 _Rp __val1 = __ct_abs<_Rp, _Tp>()(__m) / std::gcd(__m, __n); 79 _Rp __val2 = __ct_abs<_Rp, _Up>()(__n); 80 _LIBCPP_ASSERT_ARGUMENT_WITHIN_DOMAIN((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm"); 81 return __val1 * __val2; 82 } 83 84 #endif // _LIBCPP_STD_VER 85 86 _LIBCPP_END_NAMESPACE_STD 87 88 _LIBCPP_POP_MACROS 89 90 #endif // _LIBCPP___NUMERIC_GCD_LCM_H 91