>
> > And Øyvind, I don't think it's a bug that collect doesn't respect
> > Wild. It's just not implemented. Someone suggested that subs might do
> > substitutions using Wilds and I put that work into t2. And this thread
> > provided a test case for it, but doing expr.subs(W**(n+1), u*W**(n+1),
> > wild=1) failed because Idx (as it is being traversed by subs) doesn't
> > have methods that normal Basic objects do, e.g. as_base_exp(), so it
> > failed.
>
> That would be cool to have implemented, though. Or maybe some kind of lambda
> thing, so you could just say
>
> collect(expr, lambda i: i.is_Indexed, lambda=True)
>
> and it would collect all Indexed terms.
>
The lambda function is very good idea. It would be extremely flexible,
and you could also use it with wildcards:
pattern = Wild('w1')**(n + 1)
collect(expr, lambda i: i.match(pattern))
But, I think it will make the learning curve much steeper if this is the
primary way to do these things. At least I had a hard time digesting
the functional aspects of python, and it took a gsoc to finally get it
in ;-)
Øyvind
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