/*=============================================================================
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Copyright (c) 2014 Paul Fultz II
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indirect.h
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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==============================================================================*/
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#ifndef BOOST_HOF_GUARD_FUNCTION_INDIRECT_H
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#define BOOST_HOF_GUARD_FUNCTION_INDIRECT_H
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/// indirect
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/// ========
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///
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/// Description
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/// -----------
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///
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/// The `indirect` function adaptor dereferences the object before calling it.
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///
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/// Synopsis
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/// --------
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///
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/// template<class F>
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/// constexpr indirect_adaptor<F> indirect(F f);
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///
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/// Semantics
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/// ---------
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///
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/// assert(indirect(f)(xs...) == (*f)(xs...));
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///
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/// Requirements
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/// ------------
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///
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/// F must be:
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///
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/// * MoveConstructible
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/// * Dereferenceable
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///
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/// Example
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/// -------
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///
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/// #include <boost/hof.hpp>
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/// #include <cassert>
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/// #include <memory>
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/// using namespace boost::hof;
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///
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/// struct sum
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/// {
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/// template<class T, class U>
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/// T operator()(T x, U y) const
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/// {
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/// return x+y;
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/// }
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/// };
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///
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/// int main() {
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/// int r = indirect(std::make_unique<sum>())(3,2);
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/// assert(r == 5);
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/// }
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///
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#include <boost/hof/detail/delegate.hpp>
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#include <boost/hof/detail/result_of.hpp>
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#include <boost/hof/reveal.hpp>
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#include <boost/hof/always.hpp>
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#include <boost/hof/detail/move.hpp>
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#include <boost/hof/detail/make.hpp>
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#include <boost/hof/detail/static_const_var.hpp>
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namespace boost { namespace hof {
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// TODO: Support non-classes as well
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template<class F>
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struct indirect_adaptor : F
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{
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typedef indirect_adaptor fit_rewritable1_tag;
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BOOST_HOF_INHERIT_CONSTRUCTOR(indirect_adaptor, F);
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template<class... Ts>
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constexpr const F& base_function(Ts&&... xs) const noexcept
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{
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return boost::hof::always_ref(*this)(xs...);
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}
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struct failure
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: failure_for<decltype(*std::declval<F>())>
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{};
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BOOST_HOF_RETURNS_CLASS(indirect_adaptor);
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template<class... Ts>
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constexpr BOOST_HOF_SFINAE_RESULT(decltype(*std::declval<F>()), id_<Ts>...)
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operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
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(
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(*BOOST_HOF_MANGLE_CAST(const F&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
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);
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};
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template<class F>
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struct indirect_adaptor<F*>
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{
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typedef indirect_adaptor fit_rewritable1_tag;
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F* f;
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constexpr indirect_adaptor() noexcept
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{}
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constexpr indirect_adaptor(F* x) noexcept
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: f(x)
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{}
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template<class... Ts>
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constexpr F& base_function(Ts&&...) const noexcept
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{
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return *f;
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}
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struct failure
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: failure_for<F>
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{};
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BOOST_HOF_RETURNS_CLASS(indirect_adaptor);
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template<class... Ts>
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constexpr BOOST_HOF_SFINAE_RESULT(F, id_<Ts>...)
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operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS
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(
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(BOOST_HOF_MANGLE_CAST(F&)(BOOST_HOF_CONST_THIS->base_function(xs...)))(BOOST_HOF_FORWARD(Ts)(xs)...)
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);
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};
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BOOST_HOF_DECLARE_STATIC_VAR(indirect, detail::make<indirect_adaptor>);
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}} // namespace boost::hof
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#endif
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