new file

[SVN r9488]

include/boost/detail/named_template_params.hpp

@@ -0,0 +1,122 @@
+// (C) Copyright Jeremy Siek 2001. Permission to copy, use, modify,
+// sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+
+#ifndef BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP
+#define BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP
+
+#include <boost/type_traits/conversion_traits.hpp>
+#include <boost/type_traits/ice.hpp>
+
+namespace boost {
+  namespace detail {
+    
+    struct default_argument { };
+
+    struct dummy_default_gen {
+      template <class Base, class Traits>
+      struct bind {
+	typedef default_argument type;
+      };
+    };
+
+   // This class template is a workaround for MSVC.
+   template <class Gen> struct default_generator {
+     typedef detail::dummy_default_gen type;
+   };
+
+    template <class T> struct is_default { 
+      enum { value = false }; 
+      typedef boost::type_traits::no_type type;
+    };
+    template <> struct is_default<default_argument> { 
+      enum { value = true }; 
+      typedef boost::type_traits::yes_type type;
+    };
+
+    struct choose_default {
+      template <class Arg, class DefaultGen, class Base, class Traits>
+      struct bind {
+	typedef typename default_generator<DefaultGen>::type Gen;
+	typedef typename Gen::template bind<Base,Traits>::type type;
+      };
+    };
+    struct choose_arg {
+      template <class Arg, class DefaultGen, class Base, class Traits>
+      struct bind {
+	typedef Arg type;
+      };
+    };
+    template <class UseDefault>
+    struct choose_arg_or_default { typedef choose_arg type; };
+    template <>
+    struct choose_arg_or_default<boost::type_traits::yes_type> {
+      typedef choose_default type;
+    };
+    
+    template <class Arg, class DefaultGen, class Base, class Traits>
+    class resolve_default {
+      typedef typename choose_arg_or_default<
+        is_default<Arg>::type
+        >::type Selector;
+    public:
+      typedef typename Selector
+	::template bind<Arg, DefaultGen, Base, Traits>::type type;
+    };
+
+    // To differentiate an unnamed parameter from a traits generator
+    // we use is_convertible<X, iter_traits_gen_base>.
+    struct named_template_param_base { };
+    
+    // This macro assumes that there is a class named default_##TYPE
+    // defined before the application of the macro.  This class should
+    // have a single member class template named "bind" with two
+    // template parameters: the type of the class being created (e.g.,
+    // the iterator_adaptor type when creating iterator adaptors) and
+    // a traits class. The bind class should have a single typedef
+    // named "type" that produces the default for TYPE.  See
+    // boost/iterator_adaptors.hpp for an example usage.  Also,
+    // applications of this macro must be placed in namespace
+    // boost::detail.
+
+#define BOOST_NAMED_TEMPLATE_PARAM(TYPE) \
+    struct get_##TYPE##_from_named { \
+      template <class Base, class NamedParams, class Traits> \
+      struct bind { \
+          typedef typename NamedParams::traits::TYPE TYPE; \
+          typedef typename resolve_default<TYPE, \
+            default_##TYPE, Base, NamedParams>::type type; \
+      }; \
+    }; \
+    struct pass_thru_##TYPE { \
+      template <class Base, class Arg, class Traits> struct bind { \
+          typedef typename resolve_default<Arg, \
+            default_##TYPE, Base, Traits>::type type; \
+      };\
+    }; \
+    template <int NamedParam> \
+    struct get_##TYPE##_dispatch { }; \
+    template <> struct get_##TYPE##_dispatch<1> { \
+      typedef get_##TYPE##_from_named type; \
+    }; \
+    template <> struct get_##TYPE##_dispatch<0> { \
+      typedef pass_thru_##TYPE type; \
+    }; \
+    template <class Base, class X, class Traits>  \
+    class get_##TYPE { \
+      enum { is_named = is_convertible<X,named_template_param_base>::value }; \
+      typedef typename get_##TYPE##_dispatch<is_named>::type Selector; \
+    public: \
+      typedef typename Selector::template bind<Base, X, Traits>::type type; \
+    }; \
+    template <> struct default_generator<default_##TYPE> { \
+      typedef default_##TYPE type; \
+    }
+
+    
+  } // namespace detail
+} // namespace boost
+
+#endif // BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP