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75 lines
2.6 KiB
75 lines
2.6 KiB
// Copyright David Abrahams 2006. Distributed under the Boost |
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// 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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#ifndef BOOST_DETAIL_FUNCTION1_DWA200655_HPP |
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# define BOOST_DETAIL_FUNCTION1_DWA200655_HPP |
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# include <boost/concept_check.hpp> |
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# include <boost/type_traits/remove_reference.hpp> |
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# include <boost/type_traits/add_const.hpp> |
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# include <boost/mpl/apply.hpp> |
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namespace boost { namespace detail { |
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// A utility for creating unary function objects that play nicely with |
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// boost::result_of and that handle the forwarding problem. |
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// |
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// mpl::apply<F, A0>::type is expected to be a stateless function |
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// object that accepts an argument of type A0&. It is also expected |
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// to have a nested ::result_type identical to its return type. |
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template<typename F> |
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struct function1 |
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{ |
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template<typename Signature> |
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struct result |
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{}; |
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template<typename This, typename A0> |
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struct result<This(A0)> |
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{ |
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// How adding const to arguments handles rvalues. |
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// |
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// if A0 is arg0 is represents actual argument |
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// -------- ------- -------------------------- |
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// T const & T const const T lvalue |
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// T & T non-const T lvalue |
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// T const T const const T rvalue |
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// T T const non-const T rvalue |
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typedef typename remove_reference< |
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typename add_const< A0 >::type |
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>::type arg0; |
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typedef typename mpl::apply1<F, arg0>::type impl; |
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typedef typename impl::result_type type; |
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}; |
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// Handles mutable lvalues |
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template<typename A0> |
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typename result<function1(A0 &)>::type |
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operator ()(A0 &a0) const |
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{ |
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typedef typename result<function1(A0 &)>::impl impl; |
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typedef typename result<function1(A0 &)>::type type; |
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typedef A0 &arg0; |
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BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); |
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//boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); |
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return impl()(a0); |
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} |
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// Handles const lvalues and all rvalues |
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template<typename A0> |
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typename result<function1(A0 const &)>::type |
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operator ()(A0 const &a0) const |
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{ |
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typedef typename result<function1(A0 const &)>::impl impl; |
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typedef typename result<function1(A0 const &)>::type type; |
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typedef A0 const &arg0; |
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BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); |
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//boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); |
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return impl()(a0); |
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} |
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}; |
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}} // namespace boost::detail |
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#endif // BOOST_DETAIL_FUNCTION1_DWA200655_HPP
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