Re: [Boost-Users] Re: [boost] Iterator Adaptor Poll

From: Beman Dawes (bdawes_at_[hidden])
Date: 2002-07-26 13:24:20

At 11:10 AM 7/26/2002, David Abrahams wrote:

 >OK, here's my (untested) singly-linked-list iterator:

Yes! Nice! Having this would have saved me a lot of bumbling around.

How about supplying slist_node with an operator++ (and eliminating 
slist_policies::increment), so that you are illustrating the two different 
possibilities for supplying a required operation.  That was something that 
confused me initially.

Another thing that still confuses me is why you need to specify Value, but 
can let Reference, Pointer, and Distance default.  A little cometary in the 
docs which go with the example to explain the rationale for your choice of 
template parameter values would be much appreciated.

--Beman

 >typedef std::string slist_data;
 >struct slist_node
 >{
 >    slist_node* next;
 >    slist_data data;
 >};
 >
 >struct slist_policies : default_iterator_policies
 >{
 >    template <class IteratorAdaptor>
 >    void increment(IteratorAdaptor& x) {
 >        x.base() = x.base()->next;
 >    }
 >
 >    template <class IteratorAdaptor>
 >    typename IteratorAdaptor::reference dereference(IteratorAdaptor& x) {
 >        return x.base()->data;
 >    }
 >
 >    // initialize, equal covered by default policies
 >};
 >
 >typedef iterator_adaptor<slist_node*, slist_policies, slist_data,
 >category_is<std::forward_iterator_tag> > slist_iterator;
 >
 >typedef iterator_adaptor<slist_node const*, slist_policies, slist_data
 >const, category_is<std::forward_iterator_tag> > slist_const_iterator;