Re: [boost] [BGL] bundled properties and their restrictions (particularly default constructibility).

Subject: Re: [boost] [BGL] bundled properties and their restrictions (particularly default constructibility).
From: Geoff Hilton (geoff.hilton_at_[hidden])
Date: 2008-10-27 10:58:34

Geoff Hilton wrote:
> Hi, my graph uses bundled properties for both vertices and edges. Both 
> bundled properties have containers that must be of a certain size when 
> they're actually used. For testing purposes these containers were of 
> fixed size (underlying container is currently a boost::array<..>.
> 
> However the real world dictates that the size of these containers pretty 
> much must be determined at run-time as opposed to compile-time because 
> the graph is built using an external source such as a file or database 
> for example.
> 
> I know the documentation requires that bundled properties be all of 
> default constructible, assignable and copy constructible[1][2] because 
> of how the containers (as specified by selectors) store them. I'm unsure 
> as to whether or how this may effect algorithms provided by the BGL, so 
> far the only ones I've used are dijkstra_shortest_path and 
> dag_shortest_path.
> 
> Given that a custom container selector may be created and push/erase 
> must be overloaded for the given custom container (for my purposes, this 
> would be to specify a custom allocator as in the example)[3], how safe 
> would it be to say that the container selector entirely dictates the 
> restrictions in question?
> 
> If the answer is "very", presuming we weren't to change these 
> restrictions for existing provided selectors would it be possible for an 
> explicit exception to be made for custom containers and their selectors 
> (created using boost::container_gen<>)? This exception might say that 
> the restrictions in question are then dictated by the custom container.
> I figure this shouldn't affect existing user code since the current 
> restrictions are already at their most strict.
> 
> Thanks very much,
> Geoff
> 
> [1] 
> http://www.boost.org/doc/libs/1_36_0/libs/graph/doc/using_adjacency_list.html#sec:adjacency-list-properties 
> 
> [2] Doug Gregor 23/03/2005, this list.
> [3] 
> http://www.boost.org/doc/libs/1_36_0/libs/graph/doc/using_adjacency_list.html#sec:custom-storage

This is just a bump of sorts, I'm still very much in need of a reply. 
Note, in [2], I meant the boost.user list, not boost.devel.

Thanks,
Geoff