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+/*=============================================================================
+ Copyright (c) 2012 Paul Fultz II
+ partial.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_PARTIAL_H
+#define BOOST_HOF_GUARD_FUNCTION_PARTIAL_H
+
+/// partial
+/// ========
+///
+/// Description
+/// -----------
+///
+/// The `partial` function adaptor allows partial application of the function.
+/// If the function can not be called with all the parameters, it will return
+/// another function. It will repeatedly do this until the function can
+/// finally be called. By default, `partial` captures all of its variables by
+/// value, just like bind. As such all parameters must be `MoveConstructible`
+/// when the function is aprtial application. `std::ref` can be used to
+/// capture references instead.
+///
+/// Synopsis
+/// --------
+///
+/// template<class F>
+/// constexpr partial_adaptor<F> partial(F f);
+///
+/// Semantics
+/// ---------
+///
+/// assert(partial(f)(xs...)(ys...) == f(xs..., 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 == partial(sum())(1)(2));
+/// }
+///
+/// References
+/// ----------
+///
+/// * [Partial application](https://en.wikipedia.org/wiki/Partial_application)
+/// * [Currying](https://en.wikipedia.org/wiki/Currying)
+///
+
+#include <boost/hof/first_of.hpp>
+#include <boost/hof/static.hpp>
+#include <boost/hof/pipable.hpp>
+#include <boost/hof/detail/make.hpp>
+#include <boost/hof/detail/static_const_var.hpp>
+
+
+namespace boost { namespace hof {
+
+// TODO: Get rid of sequence parameter
+// Forward declare partial_adaptor, since it will be used below
+template<class F, class Pack=void >
+struct partial_adaptor;
+
+BOOST_HOF_DECLARE_STATIC_VAR(partial, detail::make<partial_adaptor>);
+
+namespace detail {
+
+template<class Derived, class F, class Pack>
+struct partial_adaptor_invoke
+{
+ template<class... Ts>
+ constexpr const F& get_function(Ts&&...) const noexcept
+ {
+ return static_cast<const F&>(static_cast<const Derived&>(*this));
+ }
+
+ template<class... Ts>
+ constexpr const Pack& get_pack(Ts&&...) const noexcept
+ {
+ return static_cast<const Pack&>(static_cast<const Derived&>(*this));
+ }
+
+ BOOST_HOF_RETURNS_CLASS(partial_adaptor_invoke);
+
+ template<class... Ts>
+ constexpr BOOST_HOF_SFINAE_RESULT
+ (
+ typename result_of<decltype(boost::hof::pack_join),
+ id_<const Pack&>,
+ result_of<decltype(boost::hof::pack_forward), id_<Ts>...>
+ >::type,
+ id_<F&&>
+ )
+ operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
+ (
+ boost::hof::pack_join
+ (
+ BOOST_HOF_MANGLE_CAST(const Pack&)(BOOST_HOF_CONST_THIS->get_pack(xs...)),
+ boost::hof::pack_forward(BOOST_HOF_FORWARD(Ts)(xs)...)
+ )
+ (BOOST_HOF_RETURNS_C_CAST(F&&)(BOOST_HOF_CONST_THIS->get_function(xs...)))
+ );
+};
+
+#ifdef _MSC_VER
+#define BOOST_HOF_PARTIAL_RETURNS(...) -> decltype(__VA_ARGS__) { return (__VA_ARGS__); }
+#else
+#define BOOST_HOF_PARTIAL_RETURNS BOOST_HOF_SFINAE_RETURNS
+#endif
+
+template<class Derived, class F, class Pack>
+struct partial_adaptor_join
+{
+ template<class... Ts>
+ constexpr const F& get_function(Ts&&...) const noexcept
+ {
+ return static_cast<const F&>(static_cast<const Derived&>(*this));
+ }
+
+ template<class... Ts>
+ constexpr const Pack& get_pack(Ts&&...) const noexcept
+ {
+ return static_cast<const Pack&>(static_cast<const Derived&>(*this));
+ }
+
+ BOOST_HOF_RETURNS_CLASS(partial_adaptor_join);
+
+ template<class... Ts, class=typename std::enable_if<
+ ((sizeof...(Ts) + Pack::fit_function_param_limit::value) < function_param_limit<F>::value)
+ >::type>
+ constexpr auto operator()(Ts&&... xs) const
+#ifdef _MSC_VER
+ // Workaround ICE on MSVC
+ noexcept(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, F&&) && noexcept(boost::hof::pack_join(std::declval<const Pack&>(), boost::hof::pack(BOOST_HOF_FORWARD(Ts)(xs)...))))
+#endif
+ BOOST_HOF_PARTIAL_RETURNS
+ (
+ boost::hof::partial
+ (
+ BOOST_HOF_RETURNS_C_CAST(F&&)(BOOST_HOF_CONST_THIS->get_function(xs...)),
+ boost::hof::pack_join(BOOST_HOF_MANGLE_CAST(const Pack&)(BOOST_HOF_CONST_THIS->get_pack(xs...)), boost::hof::pack(BOOST_HOF_FORWARD(Ts)(xs)...))
+ )
+ );
+};
+
+template<class Derived, class F>
+struct partial_adaptor_pack
+{
+
+ constexpr partial_adaptor_pack() noexcept
+ {}
+
+ 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(partial_adaptor_pack);
+
+ template<class... Ts, class=typename std::enable_if<
+ (sizeof...(Ts) < function_param_limit<F>::value)
+ >::type>
+ constexpr auto operator()(Ts&&... xs) const
+#ifdef _MSC_VER
+ // Workaround ICE on MSVC
+ noexcept(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, F&&) && noexcept(boost::hof::pack(BOOST_HOF_FORWARD(Ts)(xs)...)))
+#endif
+ BOOST_HOF_PARTIAL_RETURNS
+ (
+ boost::hof::partial
+ (
+ BOOST_HOF_RETURNS_C_CAST(F&&)(BOOST_HOF_CONST_THIS->get_function(xs...)),
+ boost::hof::pack(BOOST_HOF_FORWARD(Ts)(xs)...)
+ )
+ );
+};
+template<class F, class Pack>
+struct partial_adaptor_base
+{
+ typedef basic_first_of_adaptor
+ <
+ partial_adaptor_invoke<partial_adaptor<F, Pack>, F, Pack>,
+ partial_adaptor_join<partial_adaptor<F, Pack>, F, Pack>
+ > type;
+};
+
+template<class Derived, class F>
+struct partial_adaptor_pack_base
+{
+ typedef basic_first_of_adaptor
+ <
+ F,
+ partial_adaptor_pack<Derived, F>
+ > type;
+};
+
+}
+
+template<class F, class Pack>
+struct partial_adaptor : detail::partial_adaptor_base<F, Pack>::type, F, Pack
+{
+ typedef typename detail::partial_adaptor_base<F, Pack>::type base;
+
+ typedef partial_adaptor fit_rewritable1_tag;
+
+ template<class... Ts>
+ constexpr const F& base_function(Ts&&...) const noexcept
+ {
+ return *this;
+ }
+
+ constexpr const Pack& get_pack() const noexcept
+ {
+ return *this;
+ }
+
+ using base::operator();
+
+ BOOST_HOF_INHERIT_DEFAULT(partial_adaptor, base, F, Pack);
+
+ template<class X, class S>
+ constexpr partial_adaptor(X&& x, S&& seq)
+ BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, X&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(Pack, S&&))
+ : F(BOOST_HOF_FORWARD(X)(x)), Pack(BOOST_HOF_FORWARD(S)(seq))
+ {}
+};
+
+template<class F>
+struct partial_adaptor<F, void> : detail::partial_adaptor_pack_base<partial_adaptor<F, void>, detail::callable_base<F>>::type
+{
+ typedef typename detail::partial_adaptor_pack_base<partial_adaptor<F, void>, detail::callable_base<F>>::type base;
+
+ typedef partial_adaptor fit_rewritable1_tag;
+
+ template<class... Ts>
+ constexpr const detail::callable_base<F>& base_function(Ts&&...) const noexcept
+ {
+ return *this;
+ }
+
+ using base::operator();
+
+ BOOST_HOF_INHERIT_CONSTRUCTOR(partial_adaptor, base);
+
+};
+
+// Make partial_adaptor work with pipable_adaptor by removing its pipableness
+template<class F>
+struct partial_adaptor<pipable_adaptor<F>, void>
+: partial_adaptor<F, void>
+{
+ typedef partial_adaptor<F, void> base;
+
+ typedef partial_adaptor fit_rewritable1_tag;
+ BOOST_HOF_INHERIT_CONSTRUCTOR(partial_adaptor, base);
+};
+
+template<class F>
+struct partial_adaptor<static_<pipable_adaptor<F>>, void>
+: partial_adaptor<F, void>
+{
+ typedef partial_adaptor<F, void> base;
+
+ typedef partial_adaptor fit_rewritable1_tag;
+
+ BOOST_HOF_INHERIT_CONSTRUCTOR(partial_adaptor, base);
+};
+}} // namespace boost::hof
+
+#endif