# Inverse Adjacency Iterator Adaptor

Defined in header boost/graph/adjacency_iterator.hpp

The inverse adjacency iterator adaptor transforms an `in_edge_iterator` into an inverse adjacency iterator. That is, it takes an iterator that traverses over edges, and creates an iterator that traverses over the source vertices of those edges.

## Synopsis

    namespace boost {
      template <class Graph, class VertexDescriptor, class InEdgeIter>
      class inv_adjacency_iterator_generator {
      public:
        typedef iterator_adaptor<...> type;
      };
    }

### Example

The following is an example of how to use the `inv_adjacency_iterator_generator` class.

    #include <boost/graph/adjacency_iterator.hpp>

    class my_graph {
      // ...
      typedef ... in_edge_iterator;
      typedef ... vertex_descriptor;
      typedef boost::inv_adjacency_iterator_generator<my_graph, vertex_descriptor, in_edge_iterator>::type inv_adjacency_iterator;
      // ...
    };

### Template Parameters

Parameter | Description
--- | ---
`Graph` | The graph type, which must model Incidence Graph.
`VertexDescriptor` | This must be the same type as `graph_traits<Graph>::vertex_descriptor`. The reason why this is a template parameter is that the primary use of `inv_adjacency_iterator_generator` is inside the definition of the graph class, and in that context we can not use `graph_traits` on the not yet fully defined graph class. Default: `graph_traits<Graph>::vertex_descriptor`
`InEdgeIter` | This must be the same type as `graph_traits<Graph>::in_edge_iterator`. Default: `graph_traits<Graph>::in_edge_iterator`

### Model of

The inverse adjacency iterator adaptor (the type `inv_adjacency_iterator_generator<...>::type`) is a model of Multi-Pass Input Iterator .

### Members

The inverse adjacency iterator type implements the member functions and operators required of the Random Access Iterator concept, except that the `reference` type is the same as the `value_type` so `operator*()` returns by-value. In addition it has the following constructor:

    inv_adjacency_iterator_generator::type(const InEdgeIter& it, const Graph* g)

Revised 19 Aug 2001

© Copyright Jeremy Siek 2000. Permission to copy, use, modify, sell and distribute this document is granted provided this copyright notice appears in all copies. This document is provided "as is" without express or implied warranty, and with no claim as to its suitability for any purpose.