# IteratorConstructibleGraph

The IteratorConstructibleGraph concept describes the interface for graph types that can be constructed using a kind of edge iterator. The edge iterator can be any InputIterator that dereferences to a pair of integers (i,j), which represent an edge that should be in the graph. The two integers i and j represent vertices where 0 <= i < |V| and 0 <= j < |V|. The edge iterator's value type should be `std::pair<T,T>` (or at least be a structure that has members `first` and `second`) and the value type `T` of the pair must be convertible to the `vertices_size_type` of the graph (an integer). There are two valid expressions required by this concept, both of which are constructors. The first creates a graph object from a first/last iterator range. The second constructor also takes a first/last iterator range and in addition requires the number of vertices and number of edges. For some graph and edge iterator types the second constructor can be more efficient than the first.

### Example

The following exampe creates two graph objects from an array of edges (vertex pairs). The type `Edge*` satisfies the requirements for an InputIterator and can therefore be used to construct a graph.

      typedef ... IteratorConstructibleGraph;
      typedef boost::graph_traits<IteratorConstructibleGraph> Traits;

      typedef std::pair<Traits::vertices_size_type,
        Traits::vertices_size_type> Edge;
      Edge edge_array[] =
        { Edge(0,1), Edge(0,2), Edge(0,3), Edge(0,4), Edge(0,5),
          Edge(1, 2), Edge(1,5), Edge(1,3),
          Edge(2, 4), Edge(2,5),
          Edge(3, 2),
          Edge(4, 3), Edge(4,1),
          Edge(5, 4) };
      Edge* first = edge_array,
        last = edge_array + sizeof(edge_array)/sizeof(Edge);

      IteratorConstructibleGraph G1(first, last);
      // do something with G1 ...

      Traits::vertices_size_type size_V = 6;
      Traits::edges_size_type size_E = sizeof(edge_array)/sizeof(Edge);
      IteratorConstructibleGraph G2(first, last, size_V, size_E);
      // do something with G2 ...

### Refinement of

Graph

### Notation

`G` | is a graph type that models IteratorConstructibleGraph.
`g` | is an object of type `G`.
`first, last` | are edge iterators (see above).
`Tr` | is an object of type `graph_traits<G>`.
`n_vertices` | is an object of type `Tr::vertices_size_type`.
`n_edges` | is an object of type `Tr::edges_size_type`.

### Valid Expressions

    G g(first, last);

Construct graph object `g` given an edge range `[first,last)`.

    G g(first, last, n_vertices, n_edges);

Construct graph object `g` given an edge range `[first,last)`, the number of vertices, and the number of edges. Sometimes this constructor is more efficient than the constructor lacking the graph size information.

Copyright © 2000 | Jeremy Siek, Univ.of Notre Dame (jsiek@lsc.nd.edu) Lie-Quan Lee, Univ.of Notre Dame (llee1@lsc.nd.edu) Andrew Lumsdaine, Univ.of Notre Dame (lums@lsc.nd.edu)