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/// \file
// Range v3 library
//
// Copyright Eric Niebler 2014-present
// Copyright Casey Carter 2016
//
// Use, modification and distribution is subject to the
// Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
// Project home: https://github.com/ericniebler/range-v3
//
#ifndef RANGES_V3_ALGORITHM_SAMPLE_HPP
#define RANGES_V3_ALGORITHM_SAMPLE_HPP
#include <utility>
#include <range/v3/range_fwd.hpp>
#include <range/v3/algorithm/copy_n.hpp>
#include <range/v3/iterator/concepts.hpp>
#include <range/v3/iterator/operations.hpp>
#include <range/v3/iterator/traits.hpp>
#include <range/v3/range/access.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/range/dangling.hpp>
#include <range/v3/range/traits.hpp>
#include <range/v3/utility/random.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-algorithms
/// @{
template<typename I, typename O>
using sample_result = detail::in_out_result<I, O>;
/// \cond
namespace detail
{
template<typename I, typename S, typename O, typename Gen>
sample_result<I, O> sample_sized_impl(I first,
S last,
iter_difference_t<I> pop_size,
O out,
iter_difference_t<O> sample_size,
Gen && gen)
{
if(pop_size > 0 && sample_size > 0)
{
std::uniform_int_distribution<iter_difference_t<I>> dist;
using param_t = typename decltype(dist)::param_type;
for(; first != last; ++first)
{
if(sample_size >= pop_size)
return copy_n(std::move(first), pop_size, std::move(out));
if(dist(gen, param_t{0, --pop_size}) < sample_size)
{
*out = *first;
++out;
if(--sample_size == 0)
break;
}
}
}
return {std::move(first), std::move(out)};
}
} // namespace detail
/// \endcond
RANGES_FUNC_BEGIN(sample)
/// \brief function template \c sample
template(typename I,
typename S,
typename O,
typename Gen = detail::default_random_engine &)(
requires input_iterator<I> AND sentinel_for<S, I> AND
weakly_incrementable<O> AND indirectly_copyable<I, O> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
(random_access_iterator<O> || forward_iterator<I> ||
sized_sentinel_for<S, I>))
sample_result<I, O> RANGES_FUNC(sample)(I first,
S last,
O out,
iter_difference_t<O> const n,
Gen && gen = detail::get_random_engine())
{
if(RANGES_CONSTEXPR_IF(forward_iterator<I> || sized_sentinel_for<S, I>)) //
{
auto const k = distance(first, last);
return detail::sample_sized_impl(std::move(first),
std::move(last),
k,
std::move(out),
n,
static_cast<Gen &&>(gen));
}
else
{
// out is random-access here; calls to advance(out,n) and
// next(out,n) are O(1).
if(n > 0)
{
for(iter_difference_t<O> i = 0; i < n; (void)++i, ++first)
{
if(first == last)
{
advance(out, i);
goto done;
}
*next(out, i) = *first;
}
std::uniform_int_distribution<iter_difference_t<O>> dist;
using param_t = typename decltype(dist)::param_type;
for(auto pop_size = n; first != last; (void)++first, ++pop_size)
{
auto const i = dist(gen, param_t{0, pop_size});
if(i < n)
*next(out, i) = *first;
}
advance(out, n);
}
done:
return {std::move(first), std::move(out)};
}
}
/// \overload
template(typename I,
typename S,
typename ORng,
typename Gen = detail::default_random_engine &)(
requires input_iterator<I> AND sentinel_for<S, I> AND
weakly_incrementable<iterator_t<ORng>> AND
indirectly_copyable<I, iterator_t<ORng>> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
(forward_range<ORng> || sized_range<ORng>) AND
(random_access_iterator<iterator_t<ORng>> || forward_iterator<I> ||
sized_sentinel_for<S, I>))
sample_result<I, borrowed_iterator_t<ORng>> RANGES_FUNC(sample)(
I first,
S last,
ORng && out,
Gen && gen = detail::get_random_engine()) //
{
if(RANGES_CONSTEXPR_IF(forward_iterator<I> || sized_sentinel_for<S, I>)) //
{
auto k = distance(first, last);
return detail::sample_sized_impl(std::move(first),
std::move(last),
k,
begin(out),
distance(out),
static_cast<Gen &&>(gen));
}
else
{
return (*this)(std::move(first),
std::move(last),
begin(out),
distance(out),
static_cast<Gen &&>(gen));
}
}
/// \overload
template(typename Rng,
typename O,
typename Gen = detail::default_random_engine &)(
requires input_range<Rng> AND weakly_incrementable<O> AND
indirectly_copyable<iterator_t<Rng>, O> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
(random_access_iterator<O> || forward_range<Rng> || sized_range<Rng>))
sample_result<borrowed_iterator_t<Rng>, O> RANGES_FUNC(sample)(
Rng && rng,
O out,
iter_difference_t<O> const n,
Gen && gen = detail::get_random_engine()) //
{
if(RANGES_CONSTEXPR_IF(forward_range<Rng> || sized_range<Rng>)) //
{
return detail::sample_sized_impl(begin(rng),
end(rng),
distance(rng),
std::move(out),
n,
static_cast<Gen &&>(gen));
}
else
{
return (*this)(
begin(rng), end(rng), std::move(out), n, static_cast<Gen &&>(gen));
}
}
/// \overload
template(typename IRng,
typename ORng,
typename Gen = detail::default_random_engine &)(
requires input_range<IRng> AND range<ORng> AND
indirectly_copyable<iterator_t<IRng>, iterator_t<ORng>> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
(random_access_iterator<iterator_t<ORng>> || forward_range<IRng> ||
sized_range<IRng>) AND
(forward_range<ORng> || sized_range<ORng>))
sample_result<borrowed_iterator_t<IRng>, borrowed_iterator_t<ORng>> //
RANGES_FUNC(sample)(IRng && rng,
ORng && out,
Gen && gen = detail::get_random_engine())
{
if(RANGES_CONSTEXPR_IF(forward_range<IRng> || sized_range<IRng>)) //
{
return detail::sample_sized_impl(begin(rng),
end(rng),
distance(rng),
begin(out),
distance(out),
static_cast<Gen &&>(gen));
}
else
{
return (*this)(begin(rng),
end(rng),
begin(out),
distance(out),
static_cast<Gen &&>(gen));
}
}
RANGES_FUNC_END(sample)
namespace cpp20
{
using ranges::sample_result;
using ranges::sample;
}
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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