boost/detail/is_xxx.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_DETAIL_IS_XXX_DWA20051011_HPP
   5 # define BOOST_DETAIL_IS_XXX_DWA20051011_HPP
   6
   7 # include <boost/config.hpp>
   8 # include <boost/mpl/bool.hpp>
   9 # include <boost/preprocessor/enum_params.hpp>
  10
  11 # if defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
  12 # include <boost/type_traits/is_reference.hpp>
  13 # include <boost/type_traits/add_reference.hpp>
  14
  15 #  define BOOST_DETAIL_IS_XXX_DEF(name, qualified_name, nargs)          \
  16 template <class X_>                                                     \
  17 struct is_##name                                                        \
  18 {                                                                       \
  19     typedef char yes;                                                   \
  20     typedef char (&no)[2];                                              \
  21                                                                         \
  22     static typename add_reference<X_>::type dummy;                      \
  23                                                                         \
  24     struct helpers                                                      \
  25     {                                                                   \
  26         template < BOOST_PP_ENUM_PARAMS_Z(1, nargs, class U) >          \
  27         static yes test(                                                \
  28            qualified_name< BOOST_PP_ENUM_PARAMS_Z(1, nargs, U) >&, int  \
  29         );                                                              \
  30                                                                         \
  31         template <class U>                                              \
  32         static no test(U&, ...);                                        \
  33     };                                                                  \
  34                                                                         \
  35     BOOST_STATIC_CONSTANT(                                              \
  36         bool, value                                                     \
  37         = !is_reference<X_>::value                                      \
  38         & (sizeof(helpers::test(dummy, 0)) == sizeof(yes)));            \
  39                                                                         \
  40     typedef mpl::bool_<value> type;                                     \
  41 };
  42
  43 # else
  44
  45 #  define BOOST_DETAIL_IS_XXX_DEF(name, qualified_name, nargs)  \
  46 template <class T>                                              \
  47 struct is_##name : mpl::false_                                  \
  48 {                                                               \
  49 };                                                              \
  50                                                                 \
  51 template < BOOST_PP_ENUM_PARAMS_Z(1, nargs, class T) >          \
  52 struct is_##name<                                               \
  53    qualified_name< BOOST_PP_ENUM_PARAMS_Z(1, nargs, T) >        \
  54 >                                                               \
  55    : mpl::true_                                                 \
  56 {                                                               \
  57 };
  58
  59 # endif
  60
  61 #endif // BOOST_DETAIL_IS_XXX_DWA20051011_HPP