ceph/src/boost/libs/parameter/include/boost/parameter/binding.hpp

   1 // Copyright David Abrahams 2005. 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_PARAMETER_BINDING_DWA200558_HPP
   5 # define BOOST_PARAMETER_BINDING_DWA200558_HPP
   6
   7 # include <boost/mpl/apply.hpp>
   8 # include <boost/mpl/assert.hpp>
   9 # include <boost/mpl/and.hpp>
  10 # include <boost/parameter/aux_/result_of0.hpp>
  11 # include <boost/parameter/aux_/void.hpp>
  12 # include <boost/type_traits/is_same.hpp>
  13
  14 namespace boost { namespace parameter {
  15
  16 // A metafunction that, given an argument pack, returns the type of
  17 // the parameter identified by the given keyword.  If no such
  18 // parameter has been specified, returns Default
  19
  20 # if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
  21 template <class Parameters, class Keyword, class Default>
  22 struct binding0
  23 {
  24     typedef typename mpl::apply_wrap3<
  25         typename Parameters::binding,Keyword,Default,mpl::true_
  26     >::type type;
  27
  28     BOOST_MPL_ASSERT_NOT((
  29         mpl::and_<
  30             is_same<Default, void_>
  31           , is_same<type, void_>
  32         >
  33     ));
  34 };
  35 # endif
  36
  37 template <class Parameters, class Keyword, class Default = void_>
  38 struct binding
  39 {
  40 # if BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x564))
  41     typedef typename mpl::eval_if<
  42         mpl::is_placeholder<Parameters>
  43       , mpl::identity<int>
  44       , binding0<Parameters,Keyword,Default>
  45     >::type type;
  46 # else
  47     typedef typename mpl::apply_wrap3<
  48         typename Parameters::binding,Keyword,Default,mpl::true_
  49     >::type type;
  50
  51     BOOST_MPL_ASSERT_NOT((
  52         mpl::and_<
  53             is_same<Default, void_>
  54           , is_same<type, void_>
  55         >
  56     ));
  57 # endif
  58
  59     BOOST_MPL_AUX_LAMBDA_SUPPORT(3,binding,(Parameters,Keyword,Default))
  60 };
  61
  62 // A metafunction that, given an argument pack, returns the type of
  63 // the parameter identified by the given keyword.  If no such
  64 // parameter has been specified, returns the type returned by invoking
  65 // DefaultFn
  66 template <class Parameters, class Keyword, class DefaultFn>
  67 struct lazy_binding
  68 {
  69   typedef typename mpl::apply_wrap3<
  70       typename Parameters::binding
  71     , Keyword
  72     , typename aux::result_of0<DefaultFn>::type
  73     , mpl::true_
  74   >::type type;
  75 };
  76
  77
  78 }} // namespace boost::parameter
  79
  80 #endif // BOOST_PARAMETER_BINDING_DWA200558_HPP