1/*=============================================================================
2 Copyright (c) 2014 Paul Fultz II
3 infix.h
4 Distributed under the Boost Software License, Version 1.0. (See accompanying
5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6==============================================================================*/
7
8#ifndef BOOST_HOF_GUARD_FUNCTION_INFIX_H
9#define BOOST_HOF_GUARD_FUNCTION_INFIX_H
10
11/// infix
12/// =====
13///
14/// Description
15/// -----------
16///
17/// The `infix` function adaptor allows the function to be used as an infix
18/// operator. The operator must be placed inside the angle brackets(ie `<`
19/// and `>`).
20///
21/// Synopsis
22/// --------
23///
24/// template<class F>
25/// constexpr infix_adaptor<F> infix(F f);
26///
27/// Semantics
28/// ---------
29///
30/// assert(x <infix(f)> y == f(x, y));
31///
32/// Requirements
33/// ------------
34///
35/// F must be:
36///
37/// * [BinaryInvocable](BinaryInvocable)
38/// * MoveConstructible
39///
40/// Operator precedence
41/// -------------------
42///
43/// Infix operators have the precedence of relational operators. This means
44/// operators such as `+` or `*` have higher precedence:
45///
46/// assert((x + y <infix(f)> z) == ((x + y) <infix(f)> z));
47/// assert((x * y <infix(f)> z) == ((x * y) <infix(f)> z));
48///
49/// However, operators such as `|` or `==` have lower precedence::
50///
51/// assert((x | y <infix(f)> z) == (x | (y <infix(f)> z)));
52/// assert((x == y <infix(f)> z) == (x == (y <infix(f)> z)));
53///
54/// Also, infix operators have left-to-right associativity:
55///
56/// assert(x <infix(f)> y <infix(g)> z == ((x <infix(f)> y) <infix(g)> z));
57///
58/// Example
59/// -------
60///
61/// #include <boost/hof.hpp>
62/// #include <cassert>
63/// using namespace boost::hof;
64///
65/// struct plus_f
66/// {
67/// template<class T, class U>
68/// T operator()(T x, U y) const
69/// {
70/// return x+y;
71/// }
72/// };
73///
74/// int main() {
75/// constexpr infix_adaptor<plus_f> plus = {};
76/// int r = 3 <plus> 2;
77/// assert(r == 5);
78/// }
79///
80
81#include <boost/hof/detail/delegate.hpp>
82#include <boost/hof/detail/callable_base.hpp>
83#include <boost/hof/always.hpp>
84#include <boost/hof/reveal.hpp>
85#include <boost/hof/detail/move.hpp>
86#include <boost/hof/detail/make.hpp>
87#include <boost/hof/detail/static_const_var.hpp>
88
89namespace boost { namespace hof {
90
91namespace detail{
92template<class T, class F>
93struct postfix_adaptor : F
94{
95 T x;
96
97 template<class X, class XF>
98 constexpr postfix_adaptor(X&& xp, XF&& fp)
99 BOOST_HOF_NOEXCEPT(BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(F, XF&&) && BOOST_HOF_IS_NOTHROW_CONSTRUCTIBLE(T, X&&))
100 : F(BOOST_HOF_FORWARD(XF)(fp)), x(BOOST_HOF_FORWARD(X)(xp))
101 {}
102
103 template<class... Ts>
104 constexpr const F& base_function(Ts&&... xs) const noexcept
105 {
106 return boost::hof::always_ref(*this)(xs...);
107 }
108
109 BOOST_HOF_RETURNS_CLASS(postfix_adaptor);
110
111 template<class... Ts>
112 constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<T&&>, id_<Ts>...)
113 operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
114 (
115 (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)...)
116 );
117
118 template<class A>
119 constexpr BOOST_HOF_SFINAE_RESULT(const F&, id_<T&&>, id_<A>)
120 operator>(A&& a) const BOOST_HOF_SFINAE_RETURNS
121 (
122 (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))
123 );
124};
125
126template<class T, class F>
127constexpr postfix_adaptor<T, F> make_postfix_adaptor(T&& x, F f)
128BOOST_HOF_NOEXCEPT_CONSTRUCTIBLE(postfix_adaptor<T, F>, T&&, F&&)
129{
130 return postfix_adaptor<T, F>(BOOST_HOF_FORWARD(T)(x), static_cast<F&&>(f));
131}
132}
133
134template<class F>
135struct infix_adaptor : detail::callable_base<F>
136{
137 typedef infix_adaptor fit_rewritable1_tag;
138 BOOST_HOF_INHERIT_CONSTRUCTOR(infix_adaptor, detail::callable_base<F>);
139
140 template<class... Ts>
141 constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const noexcept
142 {
143 return boost::hof::always_ref(*this)(xs...);
144 }
145
146 template<class... Ts>
147 constexpr const detail::callable_base<F>& infix_base_function(Ts&&... xs) const noexcept
148 {
149 return boost::hof::always_ref(*this)(xs...);
150 }
151
152 BOOST_HOF_RETURNS_CLASS(infix_adaptor);
153
154 template<class... Ts>
155 constexpr auto operator()(Ts&&... xs) const BOOST_HOF_RETURNS
156 (
157 (BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
158 );
159};
160
161template<class T, class F>
162constexpr auto operator<(T&& x, const infix_adaptor<F>& i) BOOST_HOF_RETURNS
163(detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(i.base_function(x))));
164
165// TODO: Operators for static_
166
167namespace detail {
168
169template<class F>
170struct static_function_wrapper;
171
172// Operators for static_function_wrapper adaptor
173template<class T, class F>
174auto operator<(T&& x, const boost::hof::detail::static_function_wrapper<F>& f) BOOST_HOF_RETURNS
175(
176 detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(f.base_function().infix_base_function()))
177);
178
179template<class F>
180struct static_default_function;
181
182// Operators for static_default_function adaptor
183template<class T, class F>
184auto operator<(T&& x, const boost::hof::detail::static_default_function<F>&) BOOST_HOF_RETURNS
185(
186 detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), boost::hof::move(F().infix_base_function()))
187);
188}
189// This overload is needed for gcc
190template<class T, class F>
191constexpr auto operator<(T&& x, const boost::hof::reveal_adaptor<F>& f) BOOST_HOF_RETURNS
192(
193 detail::make_postfix_adaptor(BOOST_HOF_FORWARD(T)(x), f.infix_base_function())
194);
195
196BOOST_HOF_DECLARE_STATIC_VAR(infix, detail::make<infix_adaptor>);
197
198}} // namespace boost::hof
199
200#endif
201

source code of boost/libs/hof/include/boost/hof/infix.hpp