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Subject: Re: [boost] [gsoc] Interest in BGL v2?
From: Andrew Sutton (asutton.list_at_[hidden])
Date: 2011-04-01 09:30:20

>> Can you elaborate?
> Thanks Mostafa. I have the same Q.
> Back in the day Jeremy told me he thought wrapper classes could be as efficient as function wrappers, but he couldn't convince others, thus BGL is functional.  But I do remember seeing some convincing arguments against wrappers since then.

I would be very surprised if wrapper classes imposed any additional
overhead (unless they're using virtual functions).

I think Dave's argument comes from a perspective of supporting broader
applicability. If a generic algorithm requires, then you have
a very strong requirement on the type of x, and you're forced to use
wrapper classes for adaptation. If you write foo(x), then you just
required some overload of foo for x. It gives you greater freedom to
adapt the implementation to your type.

Origin has a tendency to use a more OO-style for defining individual
data structures, but uses the functional style in generic contexts.
The concepts will be defined in terms of the free functions and not
the data structures themselves.

We'd like to support the idea writing g.size() should be the same as
size(g). This lets users use OO-style when they know the type being
operated on or the functional style when they only know the concept it

> Also, do concept maps (RIP) fix this? I seem to remember some blurring between OO and functional there.

It would be interesting to see what people would do with concept maps.
At the very least it adds another choice for adaptation. Free
functions and traits, wrapper classes, and now concept maps (assuming
they show up again).


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