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215 lines
6.1 KiB
215 lines
6.1 KiB
/*============================================================================= |
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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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