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+/*=============================================================================
+ Copyright (c) 2014 Paul Fultz II
+ infix.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_INFIX_H
+#define BOOST_HOF_GUARD_FUNCTION_INFIX_H
+
+/// infix
+/// =====
+///
+/// Description
+/// -----------
+///
+/// The `infix` function adaptor allows the function to be used as an infix
+/// operator. The operator must be placed inside the angle brackets(ie `<`
+/// and `>`).
+///
+/// Synopsis
+/// --------
+///
+/// template<class F>
+/// constexpr infix_adaptor<F> infix(F f);
+///
+/// Semantics
+/// ---------
+///
+/// assert(x <infix(f)> y == f(x, y));
+///
+/// Requirements
+/// ------------
+///
+/// F must be:
+///
+/// * [BinaryInvocable](BinaryInvocable)
+/// * MoveConstructible
+///
+/// Operator precedence
+/// -------------------
+///
+/// Infix operators have the precedence of relational operators. This means
+/// operators such as `+` or `*` have higher precedence:
+///
+/// assert((x + y <infix(f)> z) == ((x + y) <infix(f)> z));
+/// assert((x * y <infix(f)> z) == ((x * y) <infix(f)> z));
+///
+/// However, operators such as `|` or `==` have lower precedence::
+///
+/// assert((x | y <infix(f)> z) == (x | (y <infix(f)> z)));
+/// assert((x == y <infix(f)> z) == (x == (y <infix(f)> z)));
+///
+/// Also, infix operators have left-to-right associativity:
+///
+/// assert(x <infix(f)> y <infix(g)> z == ((x <infix(f)> y) <infix(g)> z));
+///
+/// Example
+/// -------
+///
+/// #include <boost/hof.hpp>
+/// #include <cassert>
+/// using namespace boost::hof;
+///
+/// struct plus_f
+/// {
+/// template<class T, class U>
+/// T operator()(T x, U y) const
+/// {
+/// return x+y;
+/// }
+/// };
+///
+/// int main() {
+/// constexpr infix_adaptor<plus_f> plus = {};
+/// int r = 3 <plus> 2;
+/// assert(r == 5);
+/// }
+///
+
+#include <boost/hof/detail/delegate.hpp>
+#include <boost/hof/detail/callable_base.hpp>
+#include <boost/hof/always.hpp>
+#include <boost/hof/reveal.hpp>
+#include <boost/hof/detail/move.hpp>
+#include <boost/hof/detail/make.hpp>
+#include <boost/hof/detail/static_const_var.hpp>
+
+namespace boost { namespace hof {
+
+namespace detail{
+template<class T, class F>
+struct postfix_adaptor : F
+{
+ T x;
+
+ template<class X, class XF>
+ constexpr postfix_adaptor(X&& xp, XF&& fp)
+ BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, XF&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(T, X&&))
+ : F(BOOST_HOF_FORWARD(XF)(fp)), x(BOOST_HOF_FORWARD(X)(xp))
+ {}
+
+ template<class... Ts>
+ constexpr const F& base_function(Ts&&... xs) const noexcept
+ {
+ return boost::hof::always_ref(*this)(xs...);
+ }
+
+ BOOST_HOF_RETURNS_CLASS(postfix_adaptor);
+
+ template<class... Ts>
+ constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<T&&>, id_<Ts>...)
+ operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
+ (
+ (BOOST_HOF_MANGLE_CAST(const F&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_RETURNS_C_CAST(T&&)(BOOST_HOF_CONST_THIS->x), BOOST_HOF_FORWARD(Ts)(xs)...)
+ );
+
+ template<class A>
+ constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<T&&>, id_<A>)
+ operator>(A&& a) const BOOST_HOF_SFINAE_RETURNS
+ (
+ (BOOST_HOF_MANGLE_CAST(const F&)(BOOST_HOF_CONST_THIS->base_function(a)))(BOOST_HOF_RETURNS_C_CAST(T&&)(BOOST_HOF_CONST_THIS->x), BOOST_HOF_FORWARD(A)(a))
+ );
+};
+
+template<class T, class F>
+constexpr postfix_adaptor<T, F> make_postfix_adaptor(T&& x, F f)
+BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(postfix_adaptor<T, F>, T&&, F&&)
+{
+ return postfix_adaptor<T, F>(BOOST_HOF_FORWARD(T)(x), static_cast<F&&>(f));
+}
+}
+
+template<class F>
+struct infix_adaptor : detail::callable_base<F>
+{
+ typedef infix_adaptor fit_rewritable1_tag;
+ BOOST_HOF_INHERIT_CONSTRUCTOR(infix_adaptor, detail::callable_base<F>);
+
+ template<class... Ts>
+ constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const noexcept
+ {
+ return boost::hof::always_ref(*this)(xs...);
+ }
+
+ template<class... Ts>
+ constexpr const detail::callable_base<F>& infix_base_function(Ts&&... xs) const noexcept
+ {
+ return boost::hof::always_ref(*this)(xs...);
+ }
+
+ BOOST_HOF_RETURNS_CLASS(infix_adaptor);
+
+ template<class... Ts>
+ constexpr auto operator()(Ts&&... xs) const BOOST_HOF_RETURNS
+ (
+ (BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
+ );
+};
+
+template<class T, class F>
+constexpr auto operator<(T&& x, const infix_adaptor<F>& i) BOOST_HOF_RETURNS
+(detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(i.base_function(x))));
+
+// TODO: Operators for static_
+
+namespace detail {
+
+template<class F>
+struct static_function_wrapper;
+
+// Operators for static_function_wrapper adaptor
+template<class T, class F>
+auto operator<(T&& x, const boost::hof::detail::static_function_wrapper<F>& f) BOOST_HOF_RETURNS
+(
+ detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(f.base_function().infix_base_function()))
+);
+
+template<class F>
+struct static_default_function;
+
+// Operators for static_default_function adaptor
+template<class T, class F>
+auto operator<(T&& x, const boost::hof::detail::static_default_function<F>&) BOOST_HOF_RETURNS
+(
+ detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(F().infix_base_function()))
+);
+}
+// This overload is needed for gcc
+template<class T, class F>
+constexpr auto operator<(T&& x, const boost::hof::reveal_adaptor<F>& f) BOOST_HOF_RETURNS
+(
+ detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), f.infix_base_function())
+);
+
+BOOST_HOF_DECLARE_STATIC_VAR(infix, detail::make<infix_adaptor>);
+
+}} // namespace boost::hof
+
+#endif