[Haskell-beginners] list monad question

[Matthias Guedemann]

Thanks David,

> all3 ls = do
>   a <- ls
>   b <- ls
>   c <- ls
>   return (a,b,c)
> 
> For each element a of list ls , for each element b of the same list
> ls, and for each element c of the same list ls, make a tuple of them.
> return the list of tall the tuples.

But it is a bit more complicated. I changed the result to [a,b,c] in order to
have variable length results. I am now trying to get a  

"allN ls n" function that returns the result for the original problem with
"allN [0..5] 3" and all combinations of the form [a,b] with "allN [0..5] 2".

So basically I want a variable number of name bindings in the list
comprehension. Is this possible in a (simple) way using the list monad? Maybe
like 

allN ls n = foldr (>>=) [] (replicate n ls) >>= return 


regards,

Matthias
-- 
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Dipl. Inf. Matthias Guedemann              / __\/ _\  /__\
Computer Systems in Engineering           / /   \ \  /_\
Otto-von-Guericke Universitaet Magdeburg / /___ _\ \//__
Tel.: 0391 / 67-19359                    \____/ \__/\__/
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