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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