From: jefffaust_at_[hidden]
Date: 2007-05-28 13:25:02
Author: jefffaust
Date: 2007-05-28 13:25:01 EDT (Mon, 28 May 2007)
New Revision: 4329
URL: http://svn.boost.org/trac/boost/changeset/4329
Log:
added
Added:
sandbox/explore/boost/explore/is_assoc_iter.hpp
Added: sandbox/explore/boost/explore/is_assoc_iter.hpp
==============================================================================
--- (empty file)
+++ sandbox/explore/boost/explore/is_assoc_iter.hpp 2007-05-28 13:25:01 EDT (Mon, 28 May 2007)
@@ -0,0 +1,66 @@
+//
+// is_assoc_iter.hpp - meta function to see if an iterator is for an associative
+// container, which we assume is true if value_type is a pair.
+//
+// Copyright (c) 2007 Danny Havenith
+//
+// 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)
+//
+//
+
+#include <boost/mpl/bool.hpp>
+#include <boost/mpl/eval_if.hpp>
+
+namespace explore
+{
+ namespace detail
+ {
+ using namespace boost::mpl;
+
+ struct false_type
+ {
+ char member[100];
+ };
+
+ // crude SFINAE-and-sizeof. uses the fact that a pointer to a value type
+ // is probably different from than that of false_type. Cleaning this up would take
+ // some more LOC.
+ template< typename T>
+ typename T::value_type* has_value_func( const T &);
+
+ false_type has_value_func(...);
+
+ template <typename T>
+ T& make_t();
+
+ template< typename T>
+ struct has_value_type : bool_<
+ sizeof(false_type)
+ !=
+ sizeof(has_value_func(make_t<T>()))>
+ {};
+
+ //
+ // returns true if the value_t could be the value_type
+ // of a map of which the iterator matches iterator_t
+ //
+ template<typename T>
+ struct is_pair : false_ {};
+
+ template<typename T1, typename T2>
+ struct is_pair<std::pair<T1, T2> > : true_ {};
+
+ template<typename T>
+ struct value_type_is_pair : is_pair<typename T::value_type> {};
+ }
+
+ // an associative iterator has a value type of pair<>
+ template <typename T>
+ struct is_assoc_iter :
+ eval_if<
+ detail::has_value_type<T>,
+ detail::value_type_is_pair<T>,
+ false_
+ > {};
+}
\ No newline at end of file