[Haskell] [newbye] 'Just a'

Yuri D'Elia wavexx at yuv.info
Fri Feb 4 13:33:41 EST 2005

Hi all. I'm experimenting with haskell and its type system.
I've done a function which scans a list, and returns "Just a"
value if the element is found, or Nothing.

get :: a -> Maybe a

and implemented

getAorB :: Maybe a -> Maybe a -> a
getAorB a b = ...

a function which returns "Just (get a)" or "Just (get b)" if (get a) is
Nothing (excluding failures in both). By now, I've implemented it in
terms of pattern matching:

getAorB a b = f (get a) (get b)
    where f (Just a) Nothing = a
          f Nothing (Just a) = a

but I'd like to know if there are other possible ways to do it, possibly
without enforcing an evaluation order like pattern matching does.

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