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