boost/poly_collection/detail/functional.hpp
/* Copyright 2016-2018 Joaquin M Lopez Munoz.
* Distributed under 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)
*
* See http://www.boost.org/libs/poly_collection for library home page.
*/
#ifndef BOOST_POLY_COLLECTION_DETAIL_FUNCTIONAL_HPP
#define BOOST_POLY_COLLECTION_DETAIL_FUNCTIONAL_HPP
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/config.hpp>
#include <boost/detail/workaround.hpp>
#include <boost/mp11/integer_sequence.hpp>
#include <tuple>
#include <utility>
/* Assorted functional utilities. Much of this would be almost trivial with
* C++14 generic lambdas.
*/
#if BOOST_WORKAROUND(BOOST_MSVC,>=1910)
/* https://lists.boost.org/Archives/boost/2017/06/235687.php */
#define BOOST_POLY_COLLECTION_DEFINE_OVERLOAD_SET(name,f) \
struct name \
{ \
template<typename... Args> \
auto operator()(Args&&... args)const \
{ \
return f(std::forward<Args>(args)...); \
} \
};
#else
#define BOOST_POLY_COLLECTION_DEFINE_OVERLOAD_SET(name,f) \
struct name \
{ \
template<typename... Args> \
auto operator()(Args&&... args)const-> \
decltype(f(std::forward<Args>(args)...)) \
{ \
return f(std::forward<Args>(args)...); \
} \
};
#endif
namespace boost{
namespace poly_collection{
namespace detail{
template<typename F,typename... TailArgs>
struct tail_closure_class
{
tail_closure_class(const F& f,std::tuple<TailArgs...> t):f(f),t(t){}
template<typename... Args>
using return_type=decltype(
std::declval<F>()(std::declval<Args>()...,std::declval<TailArgs>()...));
template<typename... Args,std::size_t... I>
return_type<Args&&...> call(mp11::index_sequence<I...>,Args&&... args)
{
return f(std::forward<Args>(args)...,std::get<I>(t)...);
}
template<typename... Args>
return_type<Args&&...> operator()(Args&&... args)
{
return call(
mp11::make_index_sequence<sizeof...(TailArgs)>{},
std::forward<Args>(args)...);
}
F f;
std::tuple<TailArgs...> t;
};
template<typename F,typename... Args>
tail_closure_class<F,Args&&...> tail_closure(const F& f,Args&&... args)
{
return {f,std::forward_as_tuple(std::forward<Args>(args)...)};
}
template<typename F,typename... HeadArgs>
struct head_closure_class
{
head_closure_class(const F& f,std::tuple<HeadArgs...> t):f(f),t(t){}
template<typename... Args>
using return_type=decltype(
std::declval<F>()(std::declval<HeadArgs>()...,std::declval<Args>()...));
template<typename... Args,std::size_t... I>
return_type<Args&&...> call(mp11::index_sequence<I...>,Args&&... args)
{
return f(std::get<I>(t)...,std::forward<Args>(args)...);
}
template<typename... Args>
return_type<Args&&...> operator()(Args&&... args)
{
return call(
mp11::make_index_sequence<sizeof...(HeadArgs)>{},
std::forward<Args>(args)...);
}
F f;
std::tuple<HeadArgs...> t;
};
template<typename F,typename... Args>
head_closure_class<F,Args&&...> head_closure(const F& f,Args&&... args)
{
return {f,std::forward_as_tuple(std::forward<Args>(args)...)};
}
template<typename ReturnType,typename F>
struct cast_return_class
{
cast_return_class(const F& f):f(f){}
template<typename... Args>
ReturnType operator()(Args&&... args)const
{
return static_cast<ReturnType>(f(std::forward<Args>(args)...));
}
F f;
};
template<typename ReturnType,typename F>
cast_return_class<ReturnType,F> cast_return(const F& f)
{
return {f};
}
template<typename F>
struct deref_to_class
{
deref_to_class(const F& f):f(f){}
template<typename... Args>
auto operator()(Args&&... args)->decltype(std::declval<F>()(*args...))
{
return f(*args...);
}
F f;
};
template<typename F>
deref_to_class<F> deref_to(const F& f)
{
return {f};
}
template<typename F>
struct deref_1st_to_class
{
deref_1st_to_class(const F& f):f(f){}
template<typename Arg,typename... Args>
auto operator()(Arg&& arg,Args&&... args)
->decltype(std::declval<F>()(*arg,std::forward<Args>(args)...))
{
return f(*arg,std::forward<Args>(args)...);
}
F f;
};
template<typename F>
deref_1st_to_class<F> deref_1st_to(const F& f)
{
return {f};
}
struct transparent_equal_to
{
template<typename T,typename U>
auto operator()(T&& x,U&& y)const
noexcept(noexcept(std::forward<T>(x)==std::forward<U>(y)))
->decltype(std::forward<T>(x)==std::forward<U>(y))
{
return std::forward<T>(x)==std::forward<U>(y);
}
};
} /* namespace poly_collection::detail */
} /* namespace poly_collection */
} /* namespace boost */
#endif