[Boost-users] in_edges for a directedS adjacency_list

[sr kumar]

Hi,
Is there a reason that the in_edges are not being maintained for
a directedS adjacency_list?

A quick look through implementations of boost::detail::add_edge(*)
indicates correct maintainance for a bidirectional case, and reuse
of the out_edges for the undirected case.

I'm hopefully not missing something obvious to more enlightened
souls and would appreciate any ideas to get the in_edges correctly
for a directedS adjacency_list.

thanks,
-sr

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[Todd A. Gibson]

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.