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/*=============================================================================
Copyright (c) 2012 Paul Fultz II
pipable.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 BOOST_HOF_GUARD_FUNCTION_PIPABLE_H
#define BOOST_HOF_GUARD_FUNCTION_PIPABLE_H
/// pipable
/// =======
///
/// Description
/// -----------
///
/// The `pipable` function adaptor provides an extension method. The first
/// parameter of the function can be piped into the function using the pipe
/// `|` operator. This can be especially convenient when there are a lot of
/// nested function calls. Functions that are made pipable can still be called
/// the traditional way without piping in the first parameter.
///
/// Synopsis
/// --------
///
/// template<class F>
/// constexpr pipable_adaptor<F> pipable(F f);
///
/// Semantics
/// ---------
///
/// assert(x | pipable(f)(ys...) == f(x, ys...));
///
/// Requirements
/// ------------
///
/// F must be:
///
/// * [ConstInvocable](ConstInvocable)
/// * MoveConstructible
///
/// Example
/// -------
///
/// #include <boost/hof.hpp>
/// #include <cassert>
/// using namespace boost::hof;
///
/// struct sum
/// {
/// template<class T, class U>
/// T operator()(T x, U y) const
/// {
/// return x+y;
/// }
/// };
///
/// int main() {
/// assert(3 == (1 | pipable(sum())(2)));
/// assert(3 == pipable(sum())(1, 2));
/// }
///
/// References
/// ----------
///
/// * [Extension methods](<Extension methods>)
///
#include <boost/hof/first_of.hpp>
#include <boost/hof/pack.hpp>
#include <boost/hof/detail/delegate.hpp>
#include <boost/hof/detail/move.hpp>
#include <boost/hof/detail/make.hpp>
#include <boost/hof/detail/static_const_var.hpp>
#include <boost/hof/limit.hpp>
namespace boost { namespace hof {
template<class F>
struct pipable_adaptor;
namespace detail {
template<class F, class Pack>
struct pipe_closure : F, Pack
{
template<class X, class P>
constexpr pipe_closure(X&& fp, P&& packp)
BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, X&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(Pack, P&&))
: F(BOOST_HOF_FORWARD(X)(fp)), Pack(BOOST_HOF_FORWARD(P)(packp))
{}
template<class... Ts>
constexpr const F& base_function(Ts&&...) const noexcept
{
return *this;
}
template<class... Ts>
constexpr const Pack& get_pack(Ts&&...) const noexcept
{
return *this;
}
template<class A>
struct invoke
{
A a;
const pipe_closure * self;
template<class X>
constexpr invoke(X&& xp, const pipe_closure * selfp)
BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(A, X&&))
: a(BOOST_HOF_FORWARD(X)(xp)), self(selfp)
{}
BOOST_HOF_RETURNS_CLASS(invoke);
template<class... Ts>
constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<A>, id_<Ts>...)
operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
(BOOST_HOF_RETURNS_STATIC_CAST(const F&)(*BOOST_HOF_CONST_THIS->self)(BOOST_HOF_FORWARD(A)(a), BOOST_HOF_FORWARD(Ts)(xs)...));
};
BOOST_HOF_RETURNS_CLASS(pipe_closure);
template<class A>
constexpr BOOST_HOF_SFINAE_RESULT(const Pack&, id_<invoke<A&&>>)
operator()(A&& a) const BOOST_HOF_SFINAE_RETURNS
(BOOST_HOF_MANGLE_CAST(const Pack&)(BOOST_HOF_CONST_THIS->get_pack(a))(invoke<A&&>(BOOST_HOF_FORWARD(A)(a), BOOST_HOF_CONST_THIS)));
};
template<class F, class Pack>
constexpr auto make_pipe_closure(F f, Pack&& p) BOOST_HOF_RETURNS
(
pipe_closure<F, typename std::remove_reference<Pack>::type>(BOOST_HOF_RETURNS_STATIC_CAST(F&&)(f), BOOST_HOF_FORWARD(Pack)(p))
);
template<class Derived, class F>
struct pipe_pack
{
template<class... Ts>
constexpr const F& get_function(Ts&&...) const noexcept
{
return static_cast<const F&>(static_cast<const Derived&>(*this));
}
BOOST_HOF_RETURNS_CLASS(pipe_pack);
template<class... Ts, class=typename std::enable_if<
(sizeof...(Ts) < function_param_limit<F>::value)
>::type>
constexpr auto operator()(Ts&&... xs) const BOOST_HOF_RETURNS
(make_pipe_closure(BOOST_HOF_RETURNS_C_CAST(F&&)(BOOST_HOF_CONST_THIS->get_function(xs...)), boost::hof::pack_forward(BOOST_HOF_FORWARD(Ts)(xs)...)));
};
template<class A, class F, class Pack>
constexpr auto operator|(A&& a, const pipe_closure<F, Pack>& p) BOOST_HOF_RETURNS
(p(BOOST_HOF_FORWARD(A)(a)));
}
template<class F>
struct pipable_adaptor
: detail::basic_first_of_adaptor<detail::callable_base<F>, detail::pipe_pack<pipable_adaptor<F>, detail::callable_base<F>> >
{
typedef detail::basic_first_of_adaptor<detail::callable_base<F>, detail::pipe_pack<pipable_adaptor<F>, detail::callable_base<F>> > base;
typedef pipable_adaptor fit_rewritable_tag;
BOOST_HOF_INHERIT_CONSTRUCTOR(pipable_adaptor, base);
constexpr const detail::callable_base<F>& base_function() const noexcept
{
return *this;
}
};
template<class A, class F>
constexpr auto operator|(A&& a, const pipable_adaptor<F>& p) BOOST_HOF_RETURNS
(p(BOOST_HOF_FORWARD(A)(a)));
BOOST_HOF_DECLARE_STATIC_VAR(pipable, detail::make<pipable_adaptor>);
namespace detail {
template<class F>
struct static_function_wrapper;
// Operators for static_function_wrapper adaptor
template<class A, class F>
auto operator|(A&& a, const boost::hof::detail::static_function_wrapper<F>& f) BOOST_HOF_RETURNS
(f(BOOST_HOF_FORWARD(A)(a)));
template<class F>
struct static_default_function;
// Operators for static_default_function adaptor
template<class A, class F>
auto operator|(A&& a, const boost::hof::detail::static_default_function<F>& f) BOOST_HOF_RETURNS
(f(BOOST_HOF_FORWARD(A)(a)));
}
template<class F>
struct static_;
// Operators for static_ adaptor
template<class A, class F>
auto operator|(A&& a, static_<F> f) BOOST_HOF_RETURNS
(f.base_function().base_function()(BOOST_HOF_FORWARD(A)(a)));
}} // namespace boost::hof
#endif
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