/usr/include/range/v3/view/sample.hpp is in librange-v3-dev 0.3.5-1.
This file is owned by root:root, with mode 0o644.
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// Range v3 library
//
// 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_VIEW_SAMPLE_HPP
#define RANGES_V3_VIEW_SAMPLE_HPP
#include <meta/meta.hpp>
#include <range/v3/detail/satisfy_boost_range.hpp>
#include <range/v3/range_concepts.hpp>
#include <range/v3/view_facade.hpp>
#include <range/v3/algorithm/shuffle.hpp>
#include <range/v3/utility/compressed_pair.hpp>
#include <range/v3/utility/iterator_concepts.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/all.hpp>
#include <range/v3/view/view.hpp>
namespace ranges
{
inline namespace v3
{
/// \cond
namespace detail
{
template<typename Rng, bool = SizedSentinel<sentinel_t<Rng>, iterator_t<Rng>>::value>
class size_tracker
{
range_difference_type_t<Rng> size_;
public:
CONCEPT_ASSERT(ForwardRange<Rng>() || SizedRange<Rng>());
size_tracker() = default;
size_tracker(Rng &rng)
: size_(ranges::distance(rng))
{}
void decrement()
{
--size_;
}
range_difference_type_t<Rng> get(Rng &, iterator_t<Rng> &) const
{
return size_;
}
};
// Impl for SizedSentinel (no need to store anything)
template<typename Rng>
class size_tracker<Rng, true>
{
public:
size_tracker() = default;
size_tracker(Rng &)
{}
void decrement()
{}
range_difference_type_t<Rng> get(Rng &rng, iterator_t<Rng> const &it) const
{
return ranges::end(rng) - it;
}
};
}
/// \endcond
/// \addtogroup group-views
/// @{
// Take a random sampling from another view
template<typename Rng, typename URNG>
class sample_view
: public view_facade<sample_view<Rng, URNG>, finite>
, tagged_compressed_tuple<
tag::range(Rng),
tag::size(mutable_<range_difference_type_t<Rng>>),
tag::engine(reference_wrapper<URNG>)>
{
friend range_access;
using D = range_difference_type_t<Rng>;
using base_t = tagged_compressed_tuple<
tag::range(Rng), tag::size(mutable_<D>), tag::engine(reference_wrapper<URNG>)>;
using base_t::engine;
using base_t::range;
using base_t::size;
template<bool IsConst>
class cursor
: tagged_compressed_tuple<
tag::range(meta::const_if_c<IsConst, sample_view> *),
tag::current(iterator_t<meta::const_if_c<IsConst, Rng>>),
tag::size(detail::size_tracker<meta::const_if_c<IsConst, Rng>>)>
{
using base_t = tagged_compressed_tuple<
tag::range(meta::const_if_c<IsConst, sample_view> *),
tag::current(iterator_t<meta::const_if_c<IsConst, Rng>>),
tag::size(detail::size_tracker<meta::const_if_c<IsConst, Rng>>)>;
using base_t::current;
using base_t::range;
using base_t::size;
D pop_size()
{
RANGES_EXPECT(range());
return size().get(range()->range(), current());
}
void advance()
{
RANGES_EXPECT(range());
if(range()->size() > 0)
{
using Dist = std::uniform_int_distribution<D>;
using Param_t = typename Dist::param_type;
Dist dist{};
URNG& engine = range()->engine().get();
for(; ; ++current(), size().decrement())
{
RANGES_ASSERT(current() != ranges::end(range()->range()));
auto n = pop_size();
RANGES_EXPECT(n > 0);
const Param_t interval{ 0, n - 1 };
if(dist(engine, interval) < range()->size())
break;
}
}
}
public:
using value_type = range_value_type_t<Rng>;
using difference_type = D;
cursor() = default;
explicit cursor(meta::const_if_c<IsConst, sample_view> &rng)
: base_t{&rng, ranges::begin(rng.range()), rng.range()}
{
auto n = pop_size();
if(rng.size() > n)
rng.size() = n;
advance();
}
range_reference_t<Rng> read() const
{
return *current();
}
bool equal(default_sentinel) const
{
RANGES_EXPECT(range());
return range()->size() <= 0;
}
void next()
{
RANGES_EXPECT(range());
RANGES_EXPECT(range()->size() > 0);
--range()->size();
RANGES_ASSERT(current() != ranges::end(range()->range()));
++current();
size().decrement();
advance();
}
};
cursor<false> begin_cursor()
{
return cursor<false>{*this};
}
template<class R = Rng, CONCEPT_REQUIRES_(meta::or_<
SizedRange<R const>,
SizedSentinel<sentinel_t<R const>, iterator_t<R const>>,
ForwardRange<R const>>::value)>
cursor<true> begin_cursor() const
{
return cursor<true>{*this};
}
public:
sample_view() = default;
explicit sample_view(Rng rng, D sample_size, URNG& generator)
: base_t{std::move(rng), sample_size, generator}
{
RANGES_EXPECT(sample_size >= 0);
}
};
namespace view
{
/// Returns a random sample of a range of length `size(range)`.
class sample_fn
{
template<typename Rng, typename URNG>
using Constraint = meta::and_<
InputRange<Rng>, UniformRandomNumberGenerator<URNG>,
ConvertibleTo<
concepts::UniformRandomNumberGenerator::result_t<URNG>,
range_difference_type_t<Rng>>,
meta::or_<
SizedRange<Rng>,
SizedSentinel<sentinel_t<Rng>, iterator_t<Rng>>,
ForwardRange<Rng>>>;
friend view_access;
template<typename Size, typename URNG = detail::default_random_engine,
CONCEPT_REQUIRES_(Integral<Size>(), UniformRandomNumberGenerator<URNG>())>
static auto bind(sample_fn fn, Size n, URNG &urng = detail::get_random_engine())
RANGES_DECLTYPE_AUTO_RETURN
(
make_pipeable(std::bind(fn, std::placeholders::_1, n, bind_forward<URNG &>(urng)))
)
public:
template<typename Rng, typename URNG = detail::default_random_engine,
CONCEPT_REQUIRES_(Constraint<Rng, URNG>())>
sample_view<all_t<Rng>, URNG> operator()(
Rng && rng, range_difference_type_t<Rng> sample_size,
URNG &generator = detail::get_random_engine()) const
{
return sample_view<all_t<Rng>, URNG>{
all(static_cast<Rng&&>(rng)), sample_size, generator
};
}
#ifndef RANGES_DOXYGEN_INVOKED
template<typename Rng, typename URNG = detail::default_random_engine,
CONCEPT_REQUIRES_(!Constraint<Rng, URNG>())>
void operator()(Rng &&, URNG && = URNG{}) const
{
CONCEPT_ASSERT_MSG(InputRange<Rng>(),
"The object on which view::sample operates must satisfy the InputRange "
"concept.");
CONCEPT_ASSERT_MSG(UniformRandomNumberGenerator<URNG>(),
"The generator passed to view::sample must satisfy the "
"UniformRandomNumberGenerator concept.");
CONCEPT_ASSERT_MSG(meta::or_<
SizedRange<Rng>,
SizedSentinel<sentinel_t<Rng>, iterator_t<Rng>>,
ForwardRange<Rng>>(),
"The underlying range for view::sample must either satisfy the SizedRange"
"concept, have iterator and sentinel types that satisfy the "
"SizedSentinel concept, or be a forward range.");
CONCEPT_ASSERT_MSG(ConvertibleTo<
concepts::UniformRandomNumberGenerator::result_t<URNG>,
range_difference_type_t<Rng>>(),
"The random generator passed to view::sample has to have a return type "
"convertible to the base iterator difference type.");
}
#endif
};
/// \relates sample_fn
/// \ingroup group-views
RANGES_INLINE_VARIABLE(view<sample_fn>, sample)
}
/// @}
}
}
RANGES_SATISFY_BOOST_RANGE(::ranges::v3::sample_view)
#endif
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