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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_OVERLOAD_HPP
#define RANGES_V3_FUNCTIONAL_OVERLOAD_HPP
#include <meta/meta.hpp>
#include <concepts/concepts.hpp>
#include <range/v3/range_fwd.hpp>
#include <range/v3/functional/concepts.hpp>
#include <range/v3/functional/invoke.hpp>
#include <range/v3/utility/static_const.hpp>
#include <range/v3/detail/prologue.hpp>
namespace ranges
{
/// \addtogroup group-functional
/// @{
/// \cond
namespace detail
{
struct _id
{
template<typename T>
using invoke = T;
};
struct _ref
{
template<typename T>
using invoke = T &;
};
struct _cref
{
template<typename T>
using invoke = T const &;
};
template<typename T>
struct _bind_front
{
template<typename... Args>
using invoke = invoke_result_t<T, Args...>;
};
} // namespace detail
/// \endcond
template<typename... Ts>
struct overloaded;
template<>
struct overloaded<>
{
private:
template<typename...>
friend struct overloaded;
template<typename, typename...>
using _result_t = void;
};
template<typename First, typename... Rest>
struct overloaded<First, Rest...>
{
private:
template<typename...>
friend struct overloaded;
RANGES_NO_UNIQUE_ADDRESS
First first_;
RANGES_NO_UNIQUE_ADDRESS
overloaded<Rest...> second_;
template<typename Qual>
using _result_first = detail::_bind_front<meta::invoke<Qual, First>>;
template<typename Qual>
struct _result_second
{
template<typename... Args>
using invoke = typename overloaded<Rest...>
::template _result_t<Qual, Args...>;
};
template<typename Qual, typename... Args>
using _result_t =
meta::invoke<
meta::conditional_t<
(bool) invocable<meta::invoke<Qual, First>, Args...>,
_result_first<Qual>,
_result_second<Qual>>,
Args...>;
public:
overloaded() = default;
constexpr overloaded(First first, Rest... rest)
: first_(static_cast<First &&>(first))
, second_{static_cast<Rest &&>(rest)...}
{}
template(typename... Args)(
requires invocable<First, Args...>)
constexpr _result_t<detail::_id, Args...> operator()(Args &&... args) &&
{
return invoke((First &&) first_, (Args &&) args...);
}
template(typename... Args)(
requires (!invocable<First, Args...>) AND
invocable<overloaded<Rest...>, Args...>)
constexpr _result_t<detail::_id, Args...> operator()(Args &&... args) &&
{
return invoke((overloaded<Rest...> &&) second_, (Args &&) args...);
}
template(typename... Args)(
requires invocable<First &, Args...>)
constexpr _result_t<detail::_ref, Args...> operator()(Args &&... args) &
{
return invoke(first_, (Args &&) args...);
}
template(typename... Args)(
requires (!invocable<First &, Args...>) AND
invocable<overloaded<Rest...> &, Args...>)
constexpr _result_t<detail::_ref, Args...> operator()(Args &&... args) &
{
return invoke(second_, (Args &&) args...);
}
template(typename... Args)(
requires invocable<First const &, Args...>)
constexpr _result_t<detail::_cref, Args...> operator()(Args &&... args) const &
{
return invoke(first_, (Args &&) args...);
}
template(typename... Args)(
requires (!invocable<First const &, Args...>) AND
invocable<overloaded<Rest...> const &, Args...>)
constexpr _result_t<detail::_cref, Args...> operator()(Args &&... args) const &
{
return invoke(second_, (Args &&) args...);
}
};
struct overload_fn
{
template<typename Fn>
constexpr Fn operator()(Fn fn) const
{
return fn;
}
template<typename... Fns>
constexpr overloaded<Fns...> operator()(Fns... fns) const
{
return overloaded<Fns...>{static_cast<Fns &&>(fns)...};
}
};
/// \ingroup group-functional
/// \sa `overload_fn`
RANGES_INLINE_VARIABLE(overload_fn, overload)
/// @}
} // namespace ranges
#include <range/v3/detail/epilogue.hpp>
#endif
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