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Implement C++17 std::sample.

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This patch implements the std::sample function added to C++17 from LFTS. It
also removes the std::experimental::sample implementation which now forwards
to std::sample.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@279948 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eric Fiselier
2016-08-28 22:14:37 +00:00
parent 17c38db650
commit 917af0a073
7 changed files with 333 additions and 62 deletions
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63
include/experimental/algorithm
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@@ -58,64 +58,11 @@ _ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searc
template <class _PopulationIterator, class _SampleIterator, class _Distance,
class _UniformRandomNumberGenerator>
_LIBCPP_INLINE_VISIBILITY
_SampleIterator __sample(_PopulationIterator __first,
_PopulationIterator __last, _SampleIterator __out,
_Distance __n,
_UniformRandomNumberGenerator &&__g,
input_iterator_tag) {
_Distance __k = 0;
for (; __first != __last && __k < __n; ++__first, (void)++__k)
__out[__k] = *__first;
_Distance __sz = __k;
for (; __first != __last; ++__first, (void)++__k) {
_Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
if (__r < __sz)
__out[__r] = *__first;
}
return __out + _VSTD::min(__n, __k);
}
template <class _PopulationIterator, class _SampleIterator, class _Distance,
class _UniformRandomNumberGenerator>
_LIBCPP_INLINE_VISIBILITY
_SampleIterator __sample(_PopulationIterator __first,
_PopulationIterator __last, _SampleIterator __out,
_Distance __n,
_UniformRandomNumberGenerator &&__g,
forward_iterator_tag) {
_Distance __unsampled_sz = _VSTD::distance(__first, __last);
for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
_Distance __r =
_VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
if (__r < __n) {
*__out++ = *__first;
--__n;
}
}
return __out;
}
template <class _PopulationIterator, class _SampleIterator, class _Distance,
class _UniformRandomNumberGenerator>
_LIBCPP_INLINE_VISIBILITY
_SampleIterator sample(_PopulationIterator __first,
_PopulationIterator __last, _SampleIterator __out,
_Distance __n, _UniformRandomNumberGenerator &&__g) {
typedef typename iterator_traits<_PopulationIterator>::iterator_category
_PopCategory;
typedef typename iterator_traits<_PopulationIterator>::difference_type
_Difference;
static_assert(__is_forward_iterator<_PopulationIterator>::value ||
__is_random_access_iterator<_SampleIterator>::value,
"SampleIterator must meet the requirements of RandomAccessIterator");
typedef typename common_type<_Distance, _Difference>::type _CommonType;
_LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
return _VSTD_LFTS::__sample(
__first, __last, __out, _CommonType(__n),
_VSTD::forward<_UniformRandomNumberGenerator>(__g),
_PopCategory());
inline _LIBCPP_INLINE_VISIBILITY
_SampleIterator sample(_PopulationIterator __first, _PopulationIterator __last,
_SampleIterator __out, _Distance __n,
_UniformRandomNumberGenerator &&__g) {
return _VSTD::__sample(__first, __last, __out, __n, __g);
}
_LIBCPP_END_NAMESPACE_LFTS