python/detail/is_wrapper.hpp

0001 // Copyright David Abrahams 2004. Distributed under the Boost
0002 // Software License, Version 1.0. (See accompanying
0003 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0004 #ifndef IS_WRAPPER_DWA2004723_HPP
0005 # define IS_WRAPPER_DWA2004723_HPP
0006
0007 # include <boost/python/detail/prefix.hpp>
0008 # include <boost/mpl/bool.hpp>
0009
0010 namespace boost { namespace python {
0011
0012 template <class T> class wrapper;
0013
0014 namespace detail
0015 {
0016   typedef char (&is_not_wrapper)[2];
0017   is_not_wrapper is_wrapper_helper(...);
0018   template <class T>
0019   char is_wrapper_helper(wrapper<T> const volatile*);
0020
0021   // A metafunction returning true iff T is [derived from] wrapper<U>
0022   template <class T>
0023   struct is_wrapper
0024     : mpl::bool_<(sizeof(detail::is_wrapper_helper((T*)0)) == 1)>
0025   {};
0026
0027 }}} // namespace boost::python::detail
0028
0029 #endif // IS_WRAPPER_DWA2004723_HPP