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Diffstat (limited to 'boost/type_erasure/placeholder_of.hpp')
| -rw-r--r-- | boost/type_erasure/placeholder_of.hpp | 58 |
1 files changed, 58 insertions, 0 deletions
diff --git a/boost/type_erasure/placeholder_of.hpp b/boost/type_erasure/placeholder_of.hpp new file mode 100644 index 0000000000..8e8171898d --- /dev/null +++ b/boost/type_erasure/placeholder_of.hpp @@ -0,0 +1,58 @@ +// Boost.TypeErasure library +// +// Copyright 2011 Steven Watanabe +// +// Distributed under the Boost Software License Version 1.0. (See +// accompanying file LICENSE_1_0.txt or copy at +// http://www.boost.org/LICENSE_1_0.txt) +// +// $Id$ + +#ifndef BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED +#define BOOST_TYPE_ERASURE_PLACEHOLDER_OF_HPP_INCLUDED + +namespace boost { +namespace type_erasure { + +template<class Concept, class T> +class any; + +template<class Concept, class T> +class param; + +/** + * A metafunction returning the (const/reference qualified) placeholder + * corresponding to an @ref any. It will also work for all bases + * of @ref any, so it can be applied to the @c Base + * parameter of @ref concept_interface. + */ +template<class T> +struct placeholder_of +{ +#ifdef BOOST_TYPE_ERASURE_DOXYGEN + typedef detail::unspecified type; +#else + typedef typename ::boost::type_erasure::placeholder_of< + typename T::_boost_type_erasure_derived_type + >::type type; +#endif +}; + +/** INTERNAL ONLY */ +template<class Concept, class T> +struct placeholder_of< ::boost::type_erasure::any<Concept, T> > +{ + typedef T type; +}; + +/** INTERNAL ONLY */ +template<class Concept, class T> +struct placeholder_of< ::boost::type_erasure::param<Concept, T> > +{ + typedef T type; +}; + +} +} + +#endif |