Re: [Boost-users] [boost-users][graph] There is graph::null_vertex, but no "null_edge"!

Subject: Re: [Boost-users] [boost-users][graph] There is graph::null_vertex, but no "null_edge"!
From: al.zatv (al.zatv_at_[hidden])
Date: 2011-02-17 18:00:00

Jeremiah Willcock <jewillco_at_[hidden]> писал(а) в своём письме Fri, 18  
Feb 2011 01:47:39 +0300:
>> There is graph::null_vertex, but no "null_edge".

> It looks like you are correct.  The BGL functions that can return  
> non-existent edges return iterators instead, in which case  
> edges(g).end() is a legitimate "null" return value.  If you know the  
> graph is non-empty, you can also return std::pair<edge_descriptor,  
> bool>, returning make_pair(*edges(g).first, false) for the "not found"  
> case and make_pair(..., true) otherwise.

Thank you for answer! I did it this way (for not founded edge)
    return make_pair( false, Graph::edge_descriptor() );

Am I correct?

But, I think, it will be much better if null_edge will be added to the  
library. It can be -1 for vector containers and null for pointer-based  
descriptors, etc.