# Noob question about list comprehensions

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## Noob question about list comprehensions

 Hello,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. -Tako _______________________________________________ Haskell-Cafe mailing list [hidden email] http://www.haskell.org/mailman/listinfo/haskell-cafe
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## Re: Noob question about list comprehensions

 length [c | x <- [1..100], let c = chain x, length c > 15] 16.02.2011 12:19, Tako Schotanus пишет: > Hello, > > 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. > > -Tako > > > _______________________________________________ > Haskell-Cafe mailing list > [hidden email] > http://www.haskell.org/mailman/listinfo/haskell-cafe_______________________________________________ Haskell-Cafe mailing list [hidden email] http://www.haskell.org/mailman/listinfo/haskell-cafe
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