mirror of
https://github.com/boostorg/hof.git
synced 2026-01-26 06:32:19 +00:00
133 lines
3.6 KiB
C++
133 lines
3.6 KiB
C++
/*=============================================================================
|
|
Copyright (c) 2014 Paul Fultz II
|
|
compose.h
|
|
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)
|
|
==============================================================================*/
|
|
|
|
#ifndef FIT_GUARD_FUNCTION_COMPOSE_H
|
|
#define FIT_GUARD_FUNCTION_COMPOSE_H
|
|
|
|
/// compose
|
|
/// =======
|
|
///
|
|
/// Description
|
|
/// -----------
|
|
///
|
|
/// The `compose` function adaptor provides function composition. It produces
|
|
/// a function object that composes a set of functions, ie the output of one
|
|
/// function becomes the input of the second function. So, `compose(f, g)(0)`
|
|
/// is equivalent to `f(g(0))`.
|
|
///
|
|
///
|
|
/// Synopsis
|
|
/// --------
|
|
///
|
|
/// template<class... Fs>
|
|
/// constexpr compose_adaptor<Fs...> compose(Fs... fs);
|
|
///
|
|
/// Semantics
|
|
/// ---------
|
|
///
|
|
/// assert(compose(f, g)(xs...) == f(g(xs...)));
|
|
///
|
|
/// Requirements
|
|
/// ------------
|
|
///
|
|
/// Fs must be:
|
|
///
|
|
/// * [Callable](concepts.md#callable)
|
|
/// * MoveConstructible
|
|
///
|
|
/// Example
|
|
/// -------
|
|
///
|
|
/// struct increment
|
|
/// {
|
|
/// template<class T>
|
|
/// T operator()(T x) const
|
|
/// {
|
|
/// return x + 1;
|
|
/// }
|
|
/// };
|
|
///
|
|
/// struct decrement
|
|
/// {
|
|
/// template<class T>
|
|
/// T operator()(T x) const
|
|
/// {
|
|
/// return x - 1;
|
|
/// }
|
|
/// };
|
|
///
|
|
/// int r = compose(increment(), decrement(), increment())(3);
|
|
/// assert(r == 4);
|
|
///
|
|
|
|
#include <fit/detail/callable_base.hpp>
|
|
#include <fit/always.hpp>
|
|
#include <fit/detail/delegate.hpp>
|
|
#include <fit/detail/compressed_pair.hpp>
|
|
#include <fit/detail/join.hpp>
|
|
#include <tuple>
|
|
#include <fit/detail/move.hpp>
|
|
#include <fit/detail/make.hpp>
|
|
#include <fit/detail/static_const_var.hpp>
|
|
|
|
namespace fit { namespace detail {
|
|
|
|
template<class F1, class F2>
|
|
struct compose_kernel : detail::compressed_pair<F1, F2>
|
|
{
|
|
typedef detail::compressed_pair<F1, F2> base_type;
|
|
|
|
FIT_INHERIT_CONSTRUCTOR(compose_kernel, base_type)
|
|
|
|
FIT_RETURNS_CLASS(compose_kernel);
|
|
|
|
template<class... Ts>
|
|
constexpr FIT_SFINAE_RESULT(const F1&, result_of<const F2&, id_<Ts>...>)
|
|
operator()(Ts&&... xs) const FIT_SFINAE_RETURNS
|
|
(
|
|
FIT_MANGLE_CAST(const F1&)(FIT_CONST_THIS->first(xs...))(
|
|
FIT_MANGLE_CAST(const F2&)(FIT_CONST_THIS->second(xs...))(FIT_FORWARD(Ts)(xs)...)
|
|
)
|
|
);
|
|
};
|
|
}
|
|
|
|
template<class F, class... Fs>
|
|
struct compose_adaptor : detail::compose_kernel<detail::callable_base<F>, FIT_JOIN(compose_adaptor, detail::callable_base<Fs>...)>
|
|
{
|
|
typedef compose_adaptor fit_rewritable_tag;
|
|
typedef FIT_JOIN(compose_adaptor, detail::callable_base<Fs>...) tail;
|
|
typedef detail::compose_kernel<detail::callable_base<F>, tail> base_type;
|
|
|
|
FIT_INHERIT_DEFAULT(compose_adaptor, base_type)
|
|
|
|
template<class X, class... Xs, FIT_ENABLE_IF_CONVERTIBLE(X, detail::callable_base<F>), FIT_ENABLE_IF_CONSTRUCTIBLE(tail, Xs...)>
|
|
constexpr compose_adaptor(X&& f1, Xs&& ... fs)
|
|
: base_type(FIT_FORWARD(X)(f1), tail(FIT_FORWARD(Xs)(fs)...))
|
|
{}
|
|
};
|
|
|
|
template<class F>
|
|
struct compose_adaptor<F> : detail::callable_base<F>
|
|
{
|
|
typedef compose_adaptor fit_rewritable_tag;
|
|
|
|
FIT_INHERIT_DEFAULT(compose_adaptor, detail::callable_base<F>)
|
|
|
|
template<class X, FIT_ENABLE_IF_CONVERTIBLE(X, detail::callable_base<F>)>
|
|
constexpr compose_adaptor(X&& f1)
|
|
: detail::callable_base<F>(FIT_FORWARD(X)(f1))
|
|
{}
|
|
|
|
};
|
|
|
|
FIT_DECLARE_STATIC_VAR(compose, detail::make<compose_adaptor>);
|
|
|
|
} // namespace fit
|
|
|
|
#endif
|