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: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2011-02-17 18:21:41

On Fri, 18 Feb 2011, al.zatv wrote:

> Jeremiah Willcock <jewillco_at_[hidden]> писал(а) в своём письме Fri, 18 Feb 
> 2011 02:04:35 +0300:
>
>> On Fri, 18 Feb 2011, al.zatv wrote:
>> 
>>> 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".
>
>>> 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.
>
>> It would be, but that would be a change to base concepts that may cause
>> old graph types to fail with new algorithms that use null_edge().  What
>> does your code that may return a null edge descriptor do?  Would it be
>> possible to return an iterator instead?
>
> My code just search one specific edge in graph. Actually, I think I can 
> return an iterator. I just don't think about it. "Null edge-descriptor" was 
> more natural idea for me:).
> So, looks like absence of null-edge is small "error-in-design" of library, or 
> it was caused by some reason?

OK.  I do not know if there was a reason; it is likely that nobody thought 
they would need it when designing the library.

-- Jeremiah Willcock