[Haskell-cafe] Noob question about list comprehensions
miguelimo38 at yandex.ru
Wed Feb 16 10:24:02 CET 2011
length [c | x <- [1..100], let c = chain x, length c > 15]
16.02.2011 12:19, Tako Schotanus пишет:
> I was going through some of the tuturials and trying out different (syntactic) alternatives to the given solutions and I I got to this line:
> *length [chain x | x <- [1..100] , length (chain x) > 15]*
> Now, there's nothing wrong with it, it works of course. But the application of chain x is repeated twice and I wondered if there was a way for a guard in a list comprehension to refer to the item
> being produced?
> Like this for example (invented syntax):
> *length [@c(chain x) | x <- [1..100] , length c > 15]*
> NB: Just to make clear, I'm not asking if there is an alternative way of preventing the repetition, of course there is, I'm just wondering about this very specific case within list comprehensions.
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