Re: [Haskell-cafe] Types and hashes of hashes, trouble for a Java-programmer...

Yes, agreed. Got any clue on the original problem (except to use Data.Map)? On Mon, Apr 13, 2009 at 6:55 PM, Jason Dagit wrote:

Others have provided help to answer your question but I'd like to provide a little bit different feedback.

On Mon, Apr 13, 2009 at 8:42 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)

When you see yourself writing a function like this, you could write it like this instead: removeMaybeHash (Just ref) = ref removeMaybeHash Nothing = HashTable.new (==) (\key -> key)

Hopefully you agree this 2 line version is more clear. You could go further of course and use the function 'maybe' from the prelude, and pass the function 'id' instead of \key -> key, but I don't want to overwhelm you.

Good luck, Jason