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Implement LCM and GCD for C++17. Same code as for Library Fundamentals TS.

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git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@276751 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Marshall Clow
2016-07-26 14:29:45 +00:00
parent f3e7cacb35
commit 1c1e91d9a3
9 changed files with 426 additions and 5 deletions
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62
include/numeric
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@@ -53,6 +53,12 @@ template <class InputIterator, class OutputIterator, class BinaryOperation>
template <class ForwardIterator, class T>
void iota(ForwardIterator first, ForwardIterator last, T value);
template <class M, class N>
constexpr common_type_t<M,N> gcd(M m, N n); // C++17
template <class M, class N>
constexpr common_type_t<M,N> lcm(M m, N n); // C++17
} // std
*/
@@ -192,6 +198,62 @@ iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value_)
*__first = __value_;
}
#if _LIBCPP_STD_VER > 14
template <typename _Tp, bool _IsSigned = is_signed<_Tp>::value> struct __abs;
template <typename _Tp>
struct __abs<_Tp, true> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t >= 0 ? __t : -__t; }
};
template <typename _Tp>
struct __abs<_Tp, false> {
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp operator()(_Tp __t) const noexcept { return __t; }
};
template<class _Tp>
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
_Tp __gcd(_Tp __m, _Tp __n)
{
static_assert((!is_signed<_Tp>::value), "" );
return __n == 0 ? __m : __gcd<_Tp>(__n, __m % __n);
}
template<class _Tp, class _Up>
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
common_type_t<_Tp,_Up>
gcd(_Tp __m, _Up __n)
{
static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types");
using _Rp = common_type_t<_Tp,_Up>;
using _Wp = make_unsigned_t<_Rp>;
return static_cast<_Rp>(__gcd(static_cast<_Wp>(__abs<_Tp>()(__m)),
static_cast<_Wp>(__abs<_Up>()(__n))));
}
template<class _Tp, class _Up>
_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
common_type_t<_Tp,_Up>
lcm(_Tp __m, _Up __n)
{
static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types");
if (__m == 0 || __n == 0)
return 0;
using _Rp = common_type_t<_Tp,_Up>;
_Rp __val1 = __abs<_Tp>()(__m) / gcd(__m,__n);
_Up __val2 = __abs<_Up>()(__n);
_LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
return __val1 * __val2;
}
#endif /* _LIBCPP_STD_VER > 14 */
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_NUMERIC