Chris@16: // (C) Copyright Jeremy Siek 2001.
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: 
Chris@16: // Revision History:
Chris@16: 
Chris@16: // 04 Oct 2001   David Abrahams
Chris@16: //      Changed name of "bind" to "select" to avoid problems with MSVC.
Chris@16: 
Chris@16: #ifndef BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP
Chris@16: #define BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP
Chris@16: 
Chris@16: #include <boost/type_traits/conversion_traits.hpp>
Chris@16: #include <boost/type_traits/composite_traits.hpp> // for is_reference
Chris@16: #if defined(__BORLANDC__)
Chris@16: #include <boost/type_traits/ice.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost {
Chris@16:   namespace detail {
Chris@16:     
Chris@16:     struct default_argument { };
Chris@16: 
Chris@16:     struct dummy_default_gen {
Chris@16:       template <class Base, class Traits>
Chris@16:       struct select {
Chris@16:         typedef default_argument type;
Chris@16:       };
Chris@16:     };
Chris@16: 
Chris@16:    // This class template is a workaround for MSVC.
Chris@16:    template <class Gen> struct default_generator {
Chris@16:      typedef detail::dummy_default_gen type;
Chris@16:    };
Chris@16: 
Chris@16:     template <class T> struct is_default { 
Chris@16:       enum { value = false };  
Chris@16:       typedef type_traits::no_type type;
Chris@16:     };
Chris@16:     template <> struct is_default<default_argument> { 
Chris@16:       enum { value = true }; 
Chris@16:       typedef type_traits::yes_type type;
Chris@16:     };
Chris@16: 
Chris@16:     struct choose_default {
Chris@16:       template <class Arg, class DefaultGen, class Base, class Traits>
Chris@16:       struct select {
Chris@16:         typedef typename default_generator<DefaultGen>::type Gen;
Chris@16:         typedef typename Gen::template select<Base,Traits>::type type;
Chris@16:       };
Chris@16:     };
Chris@16:     struct choose_arg {
Chris@16:       template <class Arg, class DefaultGen, class Base, class Traits>
Chris@16:       struct select {
Chris@16:         typedef Arg type;
Chris@16:       };
Chris@16:     };
Chris@16: 
Chris@16: #if defined(__BORLANDC__)
Chris@16:     template <class UseDefault>
Chris@16:     struct choose_arg_or_default { typedef choose_arg type; };
Chris@16:     template <>
Chris@16:     struct choose_arg_or_default<type_traits::yes_type> {
Chris@16:       typedef choose_default type;
Chris@16:     };
Chris@16: #else
Chris@16:     template <bool UseDefault>
Chris@16:     struct choose_arg_or_default { typedef choose_arg type; };
Chris@16:     template <>
Chris@16:     struct choose_arg_or_default<true> {
Chris@16:       typedef choose_default type;
Chris@16:     };
Chris@16: #endif
Chris@16:     
Chris@16:     template <class Arg, class DefaultGen, class Base, class Traits>
Chris@16:     class resolve_default {
Chris@16: #if defined(__BORLANDC__)
Chris@16:       typedef typename choose_arg_or_default<typename is_default<Arg>::type>::type Selector;
Chris@16: #else
Chris@16:       // This usually works for Borland, but I'm seeing weird errors in
Chris@16:       // iterator_adaptor_test.cpp when using this method.
Chris@16:       enum { is_def = is_default<Arg>::value };
Chris@16:       typedef typename choose_arg_or_default<is_def>::type Selector;
Chris@16: #endif
Chris@16:     public:
Chris@16:       typedef typename Selector
Chris@16:         ::template select<Arg, DefaultGen, Base, Traits>::type type;
Chris@16:     };
Chris@16: 
Chris@16:     // To differentiate an unnamed parameter from a traits generator
Chris@16:     // we use is_convertible<X, iter_traits_gen_base>.
Chris@16:     struct named_template_param_base { };
Chris@16: 
Chris@16:     template <class X>
Chris@16:     struct is_named_param_list {
Chris@16:       enum { value  = is_convertible<X, named_template_param_base>::value };
Chris@16:     };
Chris@16:     
Chris@16:     struct choose_named_params {
Chris@16:       template <class Prev> struct select { typedef Prev type; };
Chris@16:     };
Chris@16:     struct choose_default_arg {
Chris@16:       template <class Prev> struct select { 
Chris@16:         typedef detail::default_argument type;
Chris@16:       };
Chris@16:     };
Chris@16: 
Chris@16:     template <bool Named> struct choose_default_dispatch_;
Chris@16:     template <> struct choose_default_dispatch_<true> {
Chris@16:       typedef choose_named_params type;
Chris@16:     };
Chris@16:     template <> struct choose_default_dispatch_<false> {
Chris@16:       typedef choose_default_arg type;
Chris@16:     };
Chris@16:     // The use of inheritance here is a Solaris Forte 6 workaround.
Chris@16:     template <bool Named> struct choose_default_dispatch
Chris@16:       : public choose_default_dispatch_<Named> { };
Chris@16: 
Chris@16:     template <class PreviousArg>
Chris@16:     struct choose_default_argument {
Chris@16:       enum { is_named = is_named_param_list<PreviousArg>::value };
Chris@16:       typedef typename choose_default_dispatch<is_named>::type Selector;
Chris@16:       typedef typename Selector::template select<PreviousArg>::type type;
Chris@16:     };
Chris@16: 
Chris@16:     // This macro assumes that there is a class named default_##TYPE
Chris@16:     // defined before the application of the macro.  This class should
Chris@16:     // have a single member class template named "select" with two
Chris@16:     // template parameters: the type of the class being created (e.g.,
Chris@16:     // the iterator_adaptor type when creating iterator adaptors) and
Chris@16:     // a traits class. The select class should have a single typedef
Chris@16:     // named "type" that produces the default for TYPE.  See
Chris@16:     // boost/iterator_adaptors.hpp for an example usage.  Also,
Chris@16:     // applications of this macro must be placed in namespace
Chris@16:     // boost::detail.
Chris@16: 
Chris@16: #define BOOST_NAMED_TEMPLATE_PARAM(TYPE) \
Chris@16:     struct get_##TYPE##_from_named { \
Chris@16:       template <class Base, class NamedParams, class Traits> \
Chris@16:       struct select { \
Chris@16:           typedef typename NamedParams::traits NamedTraits; \
Chris@16:           typedef typename NamedTraits::TYPE TYPE; \
Chris@16:           typedef typename resolve_default<TYPE, \
Chris@16:             default_##TYPE, Base, NamedTraits>::type type; \
Chris@16:       }; \
Chris@16:     }; \
Chris@16:     struct pass_thru_##TYPE { \
Chris@16:       template <class Base, class Arg, class Traits> struct select { \
Chris@16:           typedef typename resolve_default<Arg, \
Chris@16:             default_##TYPE, Base, Traits>::type type; \
Chris@16:       };\
Chris@16:     }; \
Chris@16:     template <int NamedParam> \
Chris@16:     struct get_##TYPE##_dispatch { }; \
Chris@16:     template <> struct get_##TYPE##_dispatch<1> { \
Chris@16:       typedef get_##TYPE##_from_named type; \
Chris@16:     }; \
Chris@16:     template <> struct get_##TYPE##_dispatch<0> { \
Chris@16:       typedef pass_thru_##TYPE type; \
Chris@16:     }; \
Chris@16:     template <class Base, class X, class Traits>  \
Chris@16:     class get_##TYPE { \
Chris@16:       enum { is_named = is_named_param_list<X>::value }; \
Chris@16:       typedef typename get_##TYPE##_dispatch<is_named>::type Selector; \
Chris@16:     public: \
Chris@16:       typedef typename Selector::template select<Base, X, Traits>::type type; \
Chris@16:     }; \
Chris@16:     template <> struct default_generator<default_##TYPE> { \
Chris@16:       typedef default_##TYPE type; \
Chris@16:     }
Chris@16: 
Chris@16:     
Chris@16:   } // namespace detail
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif // BOOST_DETAIL_NAMED_TEMPLATE_PARAMS_HPP