Why not use an ordered pair as the key? Regards, John A. De Goes N-BRAIN, Inc. The Evolution of Collaboration http://www.n-brain.net | 877-376-2724 x 101 On Apr 13, 2009, at 9:42 AM, John Smith wrote:
Hi, a java-programmer running into trouble while trying to learn Haskell.
I try to make a hash containing hashes but can not getting a value out of the innermost hash - I keep running into type-trouble where IO and Maybe monad is getting mixed?
My attempt:
removeMaybeHash x = case x of Just ref -> ref Nothing -> HashTable.new (==) (\key -> key)
test = do h <- HashTable.new (==) (\key -> key) h1 <- HashTable.new (==) (\key -> key) HashTable.insert h 3 h1 HashTable.insert h1 1 1000 maybeOuterHash <- HashTable.lookup h 3 res <- removeMaybe (removeMaybeHash maybeOuterHash) 1000 return res
Any clues?
In java this would be as simple as (pseudocode): h.lookup(3).lookup(1000)
Cheers,
Pedro
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