++The boost::iterator_traits class provides access to the +associated types of iterators that model the Boost Iterator Concepts, which are a +replacement for the iterator requirements in the C++ standard. +The main difference between std::iterator_traits and +boost::iterator_traits is that the iterator_category +type has been removed, and replaced with two new types: + +
+An important feature of the boost::iterator_traits is that it +is backwards compatible, i.e., it will automatically work for +iterators for which there are valid definitions of +std::iterator_traits. The old iterator_category is +mapped to the appropriate traversal and return categories. + +
+When creating a new iterator type that is meant to work with +boost::iterator_traits, you can either create a +specialization of boost::iterator_traits for your iterator +type, or you can provide all the necessary associated types as nested +typedefs. In this case, your iterator class will need to inherit from +new_iterator_base to let boost::iterator_traits know +that it will be able to find typedefs for traversal_category +and return_category in you iterator class. + +
namespace boost {
+ // Inherit from iterator_base if your iterator defines its own
+ // return_category and traversal_category. Otherwise, the "old style"
+ // iterator category will be mapped to the return_category and
+ // traversal_category.
+ struct new_iterator_base { };
+
template <typename Iterator>
struct iterator_traits
{
@@ -86,7 +131,7 @@ namespace boost {
jeremy siek
-Last modified: Sun Mar 18 17:10:26 EST 2001
+Last modified: Mon Mar 19 12:59:30 EST 2001