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216 lines
6.1 KiB
216 lines
6.1 KiB
5 years ago
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/*=============================================================================
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Copyright (c) 2012 Paul Fultz II
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pipable.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_FUNCTION_PIPABLE_H
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#define BOOST_HOF_GUARD_FUNCTION_PIPABLE_H
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/// pipable
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/// =======
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///
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/// Description
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/// -----------
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///
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/// The `pipable` function adaptor provides an extension method. The first
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/// parameter of the function can be piped into the function using the pipe
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/// `|` operator. This can be especially convenient when there are a lot of
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/// nested function calls. Functions that are made pipable can still be called
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/// the traditional way without piping in the first parameter.
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///
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/// Synopsis
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/// --------
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///
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/// template<class F>
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/// constexpr pipable_adaptor<F> pipable(F f);
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///
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/// Semantics
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/// ---------
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///
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/// assert(x | pipable(f)(ys...) == f(x, ys...));
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///
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/// Requirements
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/// ------------
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///
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/// F must be:
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///
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/// * [ConstInvocable](ConstInvocable)
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/// * MoveConstructible
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///
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/// Example
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/// -------
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///
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/// #include <boost/hof.hpp>
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/// #include <cassert>
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/// using namespace boost::hof;
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///
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/// struct sum
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/// {
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/// template<class T, class U>
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/// T operator()(T x, U y) const
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/// {
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/// return x+y;
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/// }
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/// };
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///
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/// int main() {
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/// assert(3 == (1 | pipable(sum())(2)));
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/// assert(3 == pipable(sum())(1, 2));
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/// }
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///
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/// References
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/// ----------
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///
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/// * [Extension methods](<Extension methods>)
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///
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#include <boost/hof/first_of.hpp>
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#include <boost/hof/pack.hpp>
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#include <boost/hof/detail/delegate.hpp>
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#include <boost/hof/detail/move.hpp>
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#include <boost/hof/detail/make.hpp>
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#include <boost/hof/detail/static_const_var.hpp>
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#include <boost/hof/limit.hpp>
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namespace boost { namespace hof {
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template<class F>
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struct pipable_adaptor;
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namespace detail {
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template<class F, class Pack>
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struct pipe_closure : F, Pack
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{
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template<class X, class P>
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constexpr pipe_closure(X&& fp, P&& packp)
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BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, X&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(Pack, P&&))
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: F(BOOST_HOF_FORWARD(X)(fp)), Pack(BOOST_HOF_FORWARD(P)(packp))
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{}
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template<class... Ts>
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constexpr const F& base_function(Ts&&...) const noexcept
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{
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return *this;
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}
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template<class... Ts>
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constexpr const Pack& get_pack(Ts&&...) const noexcept
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{
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return *this;
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}
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template<class A>
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struct invoke
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{
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A a;
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const pipe_closure * self;
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template<class X>
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constexpr invoke(X&& xp, const pipe_closure * selfp)
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BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(A, X&&))
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: a(BOOST_HOF_FORWARD(X)(xp)), self(selfp)
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{}
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BOOST_HOF_RETURNS_CLASS(invoke);
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template<class... Ts>
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constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<A>, id_<Ts>...)
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operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
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(BOOST_HOF_RETURNS_STATIC_CAST(const F&)(*BOOST_HOF_CONST_THIS->self)(BOOST_HOF_FORWARD(A)(a), BOOST_HOF_FORWARD(Ts)(xs)...));
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};
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BOOST_HOF_RETURNS_CLASS(pipe_closure);
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template<class A>
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constexpr BOOST_HOF_SFINAE_RESULT(const Pack&, id_<invoke<A&&>>)
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operator()(A&& a) const BOOST_HOF_SFINAE_RETURNS
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(BOOST_HOF_MANGLE_CAST(const Pack&)(BOOST_HOF_CONST_THIS->get_pack(a))(invoke<A&&>(BOOST_HOF_FORWARD(A)(a), BOOST_HOF_CONST_THIS)));
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};
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template<class F, class Pack>
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constexpr auto make_pipe_closure(F f, Pack&& p) BOOST_HOF_RETURNS
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(
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pipe_closure<F, typename std::remove_reference<Pack>::type>(BOOST_HOF_RETURNS_STATIC_CAST(F&&)(f), BOOST_HOF_FORWARD(Pack)(p))
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);
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template<class Derived, class F>
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struct pipe_pack
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{
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template<class... Ts>
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constexpr const F& get_function(Ts&&...) const noexcept
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{
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return static_cast<const F&>(static_cast<const Derived&>(*this));
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}
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BOOST_HOF_RETURNS_CLASS(pipe_pack);
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template<class... Ts, class=typename std::enable_if<
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(sizeof...(Ts) < function_param_limit<F>::value)
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>::type>
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constexpr auto operator()(Ts&&... xs) const BOOST_HOF_RETURNS
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(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)...)));
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};
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template<class A, class F, class Pack>
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constexpr auto operator|(A&& a, const pipe_closure<F, Pack>& p) BOOST_HOF_RETURNS
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(p(BOOST_HOF_FORWARD(A)(a)));
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}
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template<class F>
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struct pipable_adaptor
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: detail::basic_first_of_adaptor<detail::callable_base<F>, detail::pipe_pack<pipable_adaptor<F>, detail::callable_base<F>> >
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{
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typedef detail::basic_first_of_adaptor<detail::callable_base<F>, detail::pipe_pack<pipable_adaptor<F>, detail::callable_base<F>> > base;
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typedef pipable_adaptor fit_rewritable_tag;
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BOOST_HOF_INHERIT_CONSTRUCTOR(pipable_adaptor, base);
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constexpr const detail::callable_base<F>& base_function() const noexcept
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{
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return *this;
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}
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};
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template<class A, class F>
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constexpr auto operator|(A&& a, const pipable_adaptor<F>& p) BOOST_HOF_RETURNS
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(p(BOOST_HOF_FORWARD(A)(a)));
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BOOST_HOF_DECLARE_STATIC_VAR(pipable, detail::make<pipable_adaptor>);
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namespace detail {
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template<class F>
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struct static_function_wrapper;
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// Operators for static_function_wrapper adaptor
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template<class A, class F>
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auto operator|(A&& a, const boost::hof::detail::static_function_wrapper<F>& f) BOOST_HOF_RETURNS
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(f(BOOST_HOF_FORWARD(A)(a)));
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template<class F>
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struct static_default_function;
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// Operators for static_default_function adaptor
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template<class A, class F>
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auto operator|(A&& a, const boost::hof::detail::static_default_function<F>& f) BOOST_HOF_RETURNS
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(f(BOOST_HOF_FORWARD(A)(a)));
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}
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template<class F>
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struct static_;
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// Operators for static_ adaptor
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template<class A, class F>
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auto operator|(A&& a, static_<F> f) BOOST_HOF_RETURNS
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(f.base_function().base_function()(BOOST_HOF_FORWARD(A)(a)));
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}} // namespace boost::hof
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#endif
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