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Diffstat (limited to 'boost/hof/infix.hpp')
| -rw-r--r-- | boost/hof/infix.hpp | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/boost/hof/infix.hpp b/boost/hof/infix.hpp new file mode 100644 index 0000000000..263297d578 --- /dev/null +++ b/boost/hof/infix.hpp @@ -0,0 +1,200 @@ +/*============================================================================= + 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 |