[Haskell-cafe] comprehension generators from IO [a]'s ?
steveofar at gmail.com
Mon Dec 19 18:13:01 EST 2005
On 12/19/05, Chris Kuklewicz <haskell at list.mightyreason.com> wrote:
> Okay...that works. Sweet.
> gdc x = ListT $ getDirectoryContents x
> get3levels top = runListT $ do
> b <- gdc top
> c <- gdc $ top++('/':b)
> d <- gdc $ top++('/':b)++('/':c)
> return (b,c,d)
Yeah, that's awesome: just as readable as the comprehension
psuedo-code if not more-so. I knew some monad wizards would step out
with something nice.
Thanks for spelling out what Andrew was getting at also, it would have
been lost on me. I haven't yet ventured into using any monads but IO
yet, maybe ListT would be a good place to start.
> I feel bound to point out http://haskell.org/hawiki/ListTDoneRight which
> has more to say about the details of ListT
OK. Thanks to you both Chris and Andrew.
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