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> struct __ct_abs; 34 35 template <typename _Result, typename _Source> 36 struct __ct_abs<_Result, _Source, true> { 37 _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY 38 _Result operator()(_Source __t) const noexcept 39 { 40 if (__t >= 0) return __t; 41 if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t); 42 return -__t; 43 } 44 }; 45 46 template <typename _Result, typename _Source> 47 struct __ct_abs<_Result, _Source, false> { 48 _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY 49 _Result operator()(_Source __t) const noexcept { return __t; } 50 }; 51 52 53 template<class _Tp> 54 _LIBCPP_CONSTEXPR _LIBCPP_HIDDEN 55 _Tp __gcd(_Tp __m, _Tp __n) 56 { 57 static_assert((!is_signed<_Tp>::value), ""); 58 return __n == 0 ? __m : _VSTD::__gcd<_Tp>(__n, __m % __n); 59 } 60 61 template<class _Tp, class _Up> 62 _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY 63 common_type_t<_Tp,_Up> 64 gcd(_Tp __m, _Up __n) 65 { 66 static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types"); 67 static_assert((!is_same<__remove_cv_t<_Tp>, bool>::value), "First argument to gcd cannot be bool" ); 68 static_assert((!is_same<__remove_cv_t<_Up>, bool>::value), "Second argument to gcd cannot be bool" ); 69 using _Rp = common_type_t<_Tp,_Up>; 70 using _Wp = make_unsigned_t<_Rp>; 71 return static_cast<_Rp>(_VSTD::__gcd( 72 static_cast<_Wp>(__ct_abs<_Rp, _Tp>()(__m)), 73 static_cast<_Wp>(__ct_abs<_Rp, _Up>()(__n)))); 74 } 75 76 template<class _Tp, class _Up> 77 _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY 78 common_type_t<_Tp,_Up> 79 lcm(_Tp __m, _Up __n) 80 { 81 static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types"); 82 static_assert((!is_same<__remove_cv_t<_Tp>, bool>::value), "First argument to lcm cannot be bool" ); 83 static_assert((!is_same<__remove_cv_t<_Up>, bool>::value), "Second argument to lcm cannot be bool" ); 84 if (__m == 0 || __n == 0) 85 return 0; 86 87 using _Rp = common_type_t<_Tp,_Up>; 88 _Rp __val1 = __ct_abs<_Rp, _Tp>()(__m) / _VSTD::gcd(__m, __n); 89 _Rp __val2 = __ct_abs<_Rp, _Up>()(__n); 90 _LIBCPP_ASSERT_UNCATEGORIZED((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm"); 91 return __val1 * __val2; 92 } 93 94 #endif // _LIBCPP_STD_VER 95 96 _LIBCPP_END_NAMESPACE_STD 97 98 _LIBCPP_POP_MACROS 99 100 #endif // _LIBCPP___NUMERIC_GCD_LCM_H 101