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80643d9366
We plan to add concepts for checking that iterators actually provide what they claim to. This is to avoid people thinking that these type traits actually check the iterator requirements in more detail. Reviewed By: ldionne, #libc Spies: Mordante, libcxx-commits, wenlei Differential Revision: https://reviews.llvm.org/D150801
113 lines
4.3 KiB
C++
113 lines
4.3 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef _LIBCPP___ALGORITHM_SAMPLE_H
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#define _LIBCPP___ALGORITHM_SAMPLE_H
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#include <__algorithm/iterator_operations.h>
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#include <__algorithm/min.h>
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#include <__assert>
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#include <__config>
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#include <__iterator/distance.h>
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#include <__iterator/iterator_traits.h>
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#include <__random/uniform_int_distribution.h>
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#include <__type_traits/common_type.h>
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#include <__utility/move.h>
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#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
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# pragma GCC system_header
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#endif
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_LIBCPP_PUSH_MACROS
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#include <__undef_macros>
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_LIBCPP_BEGIN_NAMESPACE_STD
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n,
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_UniformRandomNumberGenerator& __g,
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input_iterator_tag) {
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_Distance __k = 0;
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for (; __first != __last && __k < __n; ++__first, (void) ++__k)
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__output_iter[__k] = *__first;
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_Distance __sz = __k;
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for (; __first != __last; ++__first, (void) ++__k) {
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_Distance __r = uniform_int_distribution<_Distance>(0, __k)(__g);
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if (__r < __sz)
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__output_iter[__r] = *__first;
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}
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return __output_iter + _VSTD::min(__n, __k);
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}
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n,
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_UniformRandomNumberGenerator& __g,
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forward_iterator_tag) {
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_Distance __unsampled_sz = _IterOps<_AlgPolicy>::distance(__first, __last);
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for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
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_Distance __r = uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
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if (__r < __n) {
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*__output_iter++ = *__first;
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--__n;
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}
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}
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return __output_iter;
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}
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template <class _AlgPolicy,
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class _PopulationIterator, class _PopulationSentinel, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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_LIBCPP_INLINE_VISIBILITY
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_SampleIterator __sample(_PopulationIterator __first,
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_PopulationSentinel __last, _SampleIterator __output_iter,
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_Distance __n, _UniformRandomNumberGenerator& __g) {
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_LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
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using _PopIterCategory = typename _IterOps<_AlgPolicy>::template __iterator_category<_PopulationIterator>;
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using _Difference = typename _IterOps<_AlgPolicy>::template __difference_type<_PopulationIterator>;
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using _CommonType = typename common_type<_Distance, _Difference>::type;
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return std::__sample<_AlgPolicy>(
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std::move(__first), std::move(__last), std::move(__output_iter), _CommonType(__n),
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__g, _PopIterCategory());
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}
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#if _LIBCPP_STD_VER >= 17
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template <class _PopulationIterator, class _SampleIterator, class _Distance,
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class _UniformRandomNumberGenerator>
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inline _LIBCPP_INLINE_VISIBILITY
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_SampleIterator sample(_PopulationIterator __first,
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_PopulationIterator __last, _SampleIterator __output_iter,
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_Distance __n, _UniformRandomNumberGenerator&& __g) {
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static_assert(__has_forward_iterator_category<_PopulationIterator>::value ||
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__has_random_access_iterator_category<_SampleIterator>::value,
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"SampleIterator must meet the requirements of RandomAccessIterator");
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return std::__sample<_ClassicAlgPolicy>(
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std::move(__first), std::move(__last), std::move(__output_iter), __n, __g);
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}
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#endif // _LIBCPP_STD_VER >= 17
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_LIBCPP_END_NAMESPACE_STD
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_LIBCPP_POP_MACROS
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#endif // _LIBCPP___ALGORITHM_SAMPLE_H
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