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/// \file
// Range v3 library
//
// Copyright Eric Niebler 2014-present
//
// 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_SHUFFLE_HPP
#define RANGES_V3_ALGORITHM_SHUFFLE_HPP
#include <cstdint>
#include <utility>
#include <range/v3/range_fwd.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/iterator/concepts.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/utility/swap.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-algorithms
/// @{
RANGES_FUNC_BEGIN(shuffle)
/// \brief function template \c shuffle
template(typename I, typename S, typename Gen = detail::default_random_engine &)(
requires random_access_iterator<I> AND sentinel_for<S, I> AND
permutable<I> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
convertible_to<invoke_result_t<Gen &>, iter_difference_t<I>>)
I RANGES_FUNC(shuffle)(I const first,
S const last,
Gen && gen = detail::get_random_engine()) //
{
auto mid = first;
if(mid == last)
return mid;
using D1 = iter_difference_t<I>;
using D2 =
meta::conditional_t<std::is_integral<D1>::value, D1, std::ptrdiff_t>;
std::uniform_int_distribution<D2> uid{};
using param_t = typename decltype(uid)::param_type;
while(++mid != last)
{
RANGES_ENSURE(mid - first <= PTRDIFF_MAX);
if(auto const i = uid(gen, param_t{0, D2(mid - first)}))
ranges::iter_swap(mid - i, mid);
}
return mid;
}
/// \overload
template(typename Rng, typename Gen = detail::default_random_engine &)(
requires random_access_range<Rng> AND permutable<iterator_t<Rng>> AND
uniform_random_bit_generator<std::remove_reference_t<Gen>> AND
convertible_to<invoke_result_t<Gen &>,
iter_difference_t<iterator_t<Rng>>>)
borrowed_iterator_t<Rng> //
RANGES_FUNC(shuffle)(Rng && rng, Gen && rand = detail::get_random_engine()) //
{
return (*this)(begin(rng), end(rng), static_cast<Gen &&>(rand));
}
RANGES_FUNC_END(shuffle)
namespace cpp20
{
using ranges::shuffle;
}
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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