Re: [Boost-users] in_edges for a directedS adjacency_list

From: Todd A. Gibson (tgibson_at_[hidden])
Date: 2005-07-06 22:35:03

On Wed, Jul 06, 2005 at 03:05:57PM -0700, sr kumar wrote:
> Hi,
> Is there a reason that the in_edges are not being maintained for 
> a directedS adjacency_list? 

I recently came across the following excerpt from
http://www.boost.org/libs/graph/doc/using_adjacency_list.html

Note especially the last sentence.

Directed and Undirected Adjacency Lists
---------------------------------------
The adjacency_list class can be used to represent both directed and
undirected graphs, depending on the argument passed to the Directed
template parameter. Selecting directedS or bidirectionalS choose a
directed graph, whereas undirectedS selects the representation for an
undirected graph. See Section Undirected Graphs for a description of
the difference between directed and undirected graphs in BGL. The
bidirectealS selector specifies that the graph will provide the
in_edges() function as well as the out_edges() function. This imposes
twice as much space overhead per edge, which is why in_edges() is
optional.