Comments on: mapfilter

By: willdampier

willdampier — Fri, 27 Mar 2009 04:11:53 +0000

In python I’ve found generators to be amazingly useful. I do something like this:
def mapfilter(KEY_FUN, LIST):
for this_item in LIST:
res = KEY_FUN(this_item)
if res:
yield res
This also removes any instances where KEY_FUN returns None as well. This also works well if LIST is another generator since it only evaluates the function as generator.next() is called. It really helps if my intermediate objects start causing memory errors.

By: Jacob

Jacob — Thu, 05 Mar 2009 16:05:21 +0000

I think you mean flatmap/2, but no, I wasn’t aware of it. I’d think mapfilter/2 would still be faster, but perhaps I’ll run some benchmarks to be sure. Thanks for pointing that out.

By: Gleb Peregud

Gleb Peregud — Thu, 05 Mar 2009 09:38:00 +0000

Have you looked at lists:mapflat/2? mapfilter/2 is equivalent to mapflat/2 with Fun returning [] or [X]. Though the former could be a little bit faster