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/// \file
// Range v3 library
//
// Copyright Eric Niebler 2013-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_VIEW_REPEAT_HPP
#define RANGES_V3_VIEW_REPEAT_HPP
#include <utility>
#include <range/v3/range_fwd.hpp>
#include <range/v3/iterator/unreachable_sentinel.hpp>
#include <range/v3/range/concepts.hpp>
#include <range/v3/utility/semiregular_box.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/view/facade.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-views
/// @{
// Ordinarily, a view shouldn't contain its elements. This is so that copying
// and assigning ranges is O(1), and also so that in the event of element
// mutation, all the copies of the range see the mutation the same way. The
// repeat_view *does* own its lone element, though. This is OK because:
// - O(N) copying is fine when N==1 as it is in this case, and
// - The element is immutable, so there is no potential for incorrect
// semantics.
template<typename Val>
struct repeat_view : view_facade<repeat_view<Val>, infinite>
{
private:
semiregular_box_t<Val> value_;
friend range_access;
struct cursor
{
private:
Val const * value_;
std::ptrdiff_t n_ = 0;
public:
cursor() = default;
explicit cursor(Val const & value)
: value_(std::addressof(value))
{}
Val const & read() const noexcept
{
return *value_;
}
bool equal(cursor const & that) const
{
return n_ == that.n_;
}
void next()
{
++n_;
}
void prev()
{
--n_;
}
void advance(std::ptrdiff_t d)
{
n_ += d;
}
std::ptrdiff_t distance_to(cursor const & that) const
{
return that.n_ - n_;
}
};
cursor begin_cursor() const
{
return cursor{value_};
}
unreachable_sentinel_t end_cursor() const
{
return unreachable;
}
public:
repeat_view() = default;
constexpr explicit repeat_view(Val value)
: value_(detail::move(value))
{}
};
namespace views
{
struct repeat_fn
{
template(typename Val)(
requires copy_constructible<Val>)
repeat_view<Val> operator()(Val value) const
{
return repeat_view<Val>{std::move(value)};
}
};
/// \relates repeat_fn
/// \ingroup group-views
RANGES_INLINE_VARIABLE(repeat_fn, repeat)
} // namespace views
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#include <range/v3/detail/satisfy_boost_range.hpp>
RANGES_SATISFY_BOOST_RANGE(::ranges::repeat_view)
#endif
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