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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_FUNCTIONAL_REFERENCE_WRAPPER_HPP
#define RANGES_V3_FUNCTIONAL_REFERENCE_WRAPPER_HPP
#include <type_traits>
#include <utility>
#include <meta/meta.hpp>
#include <concepts/concepts.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/utility/addressof.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-functional
/// @{
/// \cond
namespace detail
{
template<typename T>
struct reference_wrapper_
{
T * t_ = nullptr;
constexpr reference_wrapper_() = default;
constexpr reference_wrapper_(T & t) noexcept
: t_(detail::addressof(t))
{}
constexpr reference_wrapper_(T &&) = delete;
constexpr T & get() const noexcept
{
return *t_;
}
};
template<typename T>
struct reference_wrapper_<T &> : reference_wrapper_<T>
{
using reference_wrapper_<T>::reference_wrapper_;
};
template<typename T>
struct reference_wrapper_<T &&>
{
T * t_ = nullptr;
constexpr reference_wrapper_() = default;
constexpr reference_wrapper_(T && t) noexcept
: t_(detail::addressof(t))
{}
constexpr T && get() const noexcept
{
return static_cast<T &&>(*t_);
}
};
} // namespace detail
/// \endcond
// Can be used to store rvalue references in addition to lvalue references.
// Also, see: https://wg21.link/lwg2993
template<typename T>
struct reference_wrapper : private detail::reference_wrapper_<T>
{
private:
using base_ = detail::reference_wrapper_<T>;
using base_::t_;
public:
using type = meta::_t<std::remove_reference<T>>;
using reference = meta::if_<std::is_reference<T>, T, T &>;
constexpr reference_wrapper() = default;
template(typename U)(
requires (!same_as<uncvref_t<U>, reference_wrapper>) AND
constructible_from<base_, U>)
constexpr reference_wrapper(U && u) noexcept(
std::is_nothrow_constructible<base_, U>::value)
: detail::reference_wrapper_<T>{static_cast<U &&>(u)}
{}
constexpr reference get() const noexcept
{
return this->base_::get();
}
constexpr operator reference() const noexcept
{
return get();
}
template(typename...)(
requires (!std::is_rvalue_reference<T>::value)) //
constexpr operator std::reference_wrapper<type>() const noexcept
{
return {get()};
}
// clang-format off
template<typename ...Args>
constexpr auto CPP_auto_fun(operator())(Args &&...args) (const)
(
return invoke(static_cast<reference>(*t_), static_cast<Args &&>(args)...)
)
// clang-format on
};
struct ref_fn
{
template(typename T)(
requires (!is_reference_wrapper_v<T>)) //
constexpr reference_wrapper<T> operator()(T & t) const
{
return {t};
}
/// \overload
template<typename T>
constexpr reference_wrapper<T> operator()(reference_wrapper<T> t) const
{
return t;
}
/// \overload
template<typename T>
constexpr reference_wrapper<T> operator()(std::reference_wrapper<T> t) const
{
return {t.get()};
}
};
/// \ingroup group-functional
/// \sa `ref_fn`
RANGES_INLINE_VARIABLE(ref_fn, ref)
template<typename T>
using ref_t = decltype(ref(std::declval<T>()));
struct unwrap_reference_fn
{
template<typename T>
constexpr T && operator()(T && t) const noexcept
{
return static_cast<T &&>(t);
}
/// \overload
template<typename T>
constexpr typename reference_wrapper<T>::reference operator()(reference_wrapper<T> t) const
noexcept
{
return t.get();
}
/// \overload
template<typename T>
constexpr T & operator()(std::reference_wrapper<T> t) const noexcept
{
return t.get();
}
/// \overload
template<typename T>
constexpr T & operator()(ref_view<T> t) const noexcept
{
return t.base();
}
};
/// \ingroup group-functional
/// \sa `unwrap_reference_fn`
RANGES_INLINE_VARIABLE(unwrap_reference_fn, unwrap_reference)
template<typename T>
using unwrap_reference_t = decltype(unwrap_reference(std::declval<T>()));
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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