1 | // Copyright David Abrahams 2006. Distributed under the Boost |
2 | // Software License, Version 1.0. (See accompanying |
3 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) |
4 | #ifndef BOOST_DETAIL_FUNCTION1_DWA200655_HPP |
5 | # define BOOST_DETAIL_FUNCTION1_DWA200655_HPP |
6 | |
7 | # include <boost/concept_check.hpp> |
8 | # include <boost/type_traits/remove_reference.hpp> |
9 | # include <boost/type_traits/add_const.hpp> |
10 | # include <boost/mpl/apply.hpp> |
11 | |
12 | namespace boost { namespace detail { |
13 | |
14 | // A utility for creating unary function objects that play nicely with |
15 | // boost::result_of and that handle the forwarding problem. |
16 | // |
17 | // mpl::apply<F, A0>::type is expected to be a stateless function |
18 | // object that accepts an argument of type A0&. It is also expected |
19 | // to have a nested ::result_type identical to its return type. |
20 | template<typename F> |
21 | struct function1 |
22 | { |
23 | template<typename Signature> |
24 | struct result |
25 | {}; |
26 | |
27 | template<typename This, typename A0> |
28 | struct result<This(A0)> |
29 | { |
30 | // How adding const to arguments handles rvalues. |
31 | // |
32 | // if A0 is arg0 is represents actual argument |
33 | // -------- ------- -------------------------- |
34 | // T const & T const const T lvalue |
35 | // T & T non-const T lvalue |
36 | // T const T const const T rvalue |
37 | // T T const non-const T rvalue |
38 | typedef typename remove_reference< |
39 | typename add_const< A0 >::type |
40 | >::type arg0; |
41 | |
42 | typedef typename mpl::apply1<F, arg0>::type impl; |
43 | typedef typename impl::result_type type; |
44 | }; |
45 | |
46 | // Handles mutable lvalues |
47 | template<typename A0> |
48 | typename result<function1(A0 &)>::type |
49 | operator ()(A0 &a0) const |
50 | { |
51 | typedef typename result<function1(A0 &)>::impl impl; |
52 | typedef typename result<function1(A0 &)>::type type; |
53 | typedef A0 &arg0; |
54 | BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); |
55 | //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); |
56 | return impl()(a0); |
57 | } |
58 | |
59 | // Handles const lvalues and all rvalues |
60 | template<typename A0> |
61 | typename result<function1(A0 const &)>::type |
62 | operator ()(A0 const &a0) const |
63 | { |
64 | typedef typename result<function1(A0 const &)>::impl impl; |
65 | typedef typename result<function1(A0 const &)>::type type; |
66 | typedef A0 const &arg0; |
67 | BOOST_CONCEPT_ASSERT((UnaryFunction<impl, type, arg0>)); |
68 | //boost::function_requires<UnaryFunctionConcept<impl, type, arg0> >(); |
69 | return impl()(a0); |
70 | } |
71 | }; |
72 | |
73 | }} // namespace boost::detail |
74 | |
75 | #endif // BOOST_DETAIL_FUNCTION1_DWA200655_HPP |
76 | |