boost/hof/mutable.hpp

0001 /*=============================================================================
0002     Copyright (c) 2014 Paul Fultz II
0003     mutable.h
0004     Distributed under the Boost Software License, Version 1.0. (See accompanying
0005     file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 ==============================================================================*/
0007
0008 #ifndef BOOST_HOF_GUARD_FUNCTION_MUTABLE_H
0009 #define BOOST_HOF_GUARD_FUNCTION_MUTABLE_H
0010
0011 /// mutable
0012 /// =======
0013 ///
0014 /// Description
0015 /// -----------
0016 ///
0017 /// The `mutable` function adaptor allows using a non-const function object
0018 /// inside of a const-function object. In Fit, all the function adaptors use
0019 /// `const` call overloads, so if there is a function that has a non-const
0020 /// call operator, it couldn't be used directly. So, `mutable_` allows the
0021 /// function to be used inside of the call operator.
0022 ///
0023 /// NOTE: This function should be used with caution since many functions are
0024 /// copied, so relying on some internal shared state can be error-prone.
0025 ///
0026 /// Synopsis
0027 /// --------
0028 ///
0029 ///     template<class F>
0030 ///     mutable_adaptor<F> mutable_(F f)
0031 ///
0032 /// Requirements
0033 /// ------------
0034 ///
0035 /// F must be:
0036 ///
0037 /// * [MutableFunctionObject](MutableFunctionObject)
0038 /// * MoveConstructible
0039 ///
0040
0041 #include <boost/hof/detail/result_of.hpp>
0042 #include <boost/hof/detail/delegate.hpp>
0043 #include <boost/hof/detail/move.hpp>
0044 #include <boost/hof/detail/make.hpp>
0045 #include <boost/hof/detail/static_const_var.hpp>
0046
0047 namespace boost { namespace hof {
0048
0049 template<class F>
0050 struct mutable_adaptor
0051 {
0052     mutable F f;
0053
0054     BOOST_HOF_DELEGATE_CONSTRUCTOR(mutable_adaptor, F, f);
0055
0056     BOOST_HOF_RETURNS_CLASS(mutable_adaptor);
0057
0058     template<class... Ts>
0059     BOOST_HOF_SFINAE_RESULT(F, id_<Ts>...)
0060     operator()(Ts&&... xs) const BOOST_HOF_SFINAE_RETURNS(BOOST_HOF_CONST_THIS->f(BOOST_HOF_FORWARD(Ts)(xs)...));
0061 };
0062
0063 BOOST_HOF_DECLARE_STATIC_VAR(mutable_, detail::make<mutable_adaptor>);
0064
0065 }} // namespace boost::hof
0066
0067
0068 #endif