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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