ceph/src/boost/libs/accumulators/include/boost/accumulators/numeric/detail/function1.hpp

   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