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
12namespace 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.
20template<typename F>
21struct 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

source code of include/boost/accumulators/numeric/detail/function1.hpp