Re: [Boost-users] [BGL] requirements on bundled properties

From: Elvanör (elvanor2004_at_[hidden])
Date: 2005-03-19 16:16:23

In addition to my last question, I wonder what are the type 
requirements for the bundled properties. Because I've had quite a few 
compiler errors, and as far as I can tell from these errors, it seems 
to me that a type used for bundled properties must be (at least) 
Assignable, and (that's even stranger for me) Default Constructible, 
since I had complains about missing default constructors and member 
references (which are not assignable).

Can someone confirms this is true? If yes, this should also be 
documented somewhere...

Jean-Noël Rivasseau

ps: I have almost no idea of how a graph is stored (internally) when 
using the BGL. But the errors seem to be linked with the type of 
containers chosen for the vertex and out-edges list (in an 
adjacency_list class). For example I had these errors when using vecS, 
but if I switch to mapS, I have only the Default Constructible error 
(not the Assignable requirement, strange...)

So the bundled properties are also stored depending on the containers 
you choose?

(as for my previous question, I realised after all that, that it's 
maybe not a good idea to have references as bundled properties, as they 
seem to be stored in containers, and having references in containers of 
the STL is a bad thing (because, once again, they are not Assignable). 
Any comments?)

> Hi.
>
>
>>> Any help would be appreciated, and I still think the documentation 
>>> should mention how to get the type of the bundled properties.
>>
>> You're absolutely correct. I've just added the aforementioned traits 
>> with some documentation for them (within the description of bundled 
>> properties).
>
> I guess all of this is in the CVS, of course... I wondered also if 
> there was a way to download all of the boost documentation (HTML 
> format) for offline browsing, rather than going to the web site every 
> time (maybe this is intentionalk though). I mean, a way different than 
> downloading the CVS documentation.
>
> I have yet a new question: is it possible to have, as a bundled 
> property, references to objects and not just the object themselves ?
>
> IE,
>
> 	typedef adjacency_list<mapS, vecS, undirectedS, myClass > Graph;
>
> works, but I can't manage to have:
>
> 	typedef adjacency_list<mapS, vecS, undirectedS, myClass &> Graph;
>
> (A pointer, though, is ok as I have noted on one of my earlier mails).
>
> I have noted, though, that function such as 
> add_vertex(const VertexProperties& p, adjacency_list& g) do take a 
> reference to a VertexProperties. So should I assume that if I 
> construct my graph in this way (via use of add_vertex, etc...) my 
> bundled properties will just be references, ie, no copy construction 
> will occur ( and after running my graph algorithms, the modifications 
> on the bundled properties will still be accessible)?
>
> Jean-Noël
>
>
>
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