Re: [boost] [gsoc] Interest in BGL v2?

Subject: Re: [boost] [gsoc] Interest in BGL v2?
From: Andrew Sutton (asutton.list_at_[hidden])
Date: 2011-03-28 19:45:26

> If you're referring to adjacency_list, then I can only say that
> generative data structures pretty much always feel like
> metaprograms... because they _are_ metaprograms.
>
> Are you planning to move away from generative programming in BGLv2?

With regards to the adjacency list, that's the plan for Origin.
Whether or not the rest of the Boost community likes the approach
remains to be seen :)

It wouldn't be hard to write a generative wrapper around a set of
specific data structures to achieve a similar affect. If it was felt
that such a wrapper was needed. It's not high on the list of my
priorities.

>> This is no good since a meta-program generates types that may model
>> one of many concepts.
>
> In what way does that make it "no good?"

I think that's a typo, "not good", which is somehow less condemning
than "no good" :)

The argument comes from a usability perspective. If I want to use a
data structure, I expect it to work a certain way---to have a specific
interface with guaranteed behaviors. Generative data structures like
the adjacency list don't fit that model. All of the generated
implementations may be AdjacencyLists, but they're all refinements in
one way or another. One side effect of this is conditional document
dependent on the choice of selector arguments.

Basically, it's a metaprogram masquerading as a data structure, which
I perceive as not great. I'm sure there are plenty of people who will
disagree.

>> Another feature that has been on BGL's want list is the
>> implementation of algorithm objects.
>
> For example?

Just a class that wraps the algorithm. There are several in the BGL.
The technique offers a little more flexibility when the number of
parameters is large.

Andrew