Re: [Boost-users] BGL: using an edge_descriptor as key in a map

From: Douglas Gregor (gregod_at_[hidden])
Date: 2004-05-11 09:31:12

On Tuesday 11 May 2004 05:59 am, boost_at_[hidden] wrote:
> Hi,
> is it possible to use an edge_descriptor
> (boost::graph_traits<G>::edge_descriptor) as key in a map?

In general, no. Edge descriptors can typically only be compared via == and !=. 
One notable exception is when the edge list type is "vecS" in an 
adjacent_list, because those edge descriptors can be used as integral types.

> I intend to write a visitor class which sets a boolean to each edge, and
> therefore I need the edge as key.

Common ways to do this include using internal properties and maintaining your 
own edge_index (internal) property so that you can build property maps out of 
vectors.

        Doug