While we're at it, the second pattern match is superfluous. Once you
take out nonempty lists from the list type, the only thing left is an
empty one!
unique :: Eq a => [a] -> [a]
unique (x:xs) = x : (unique . filter (/= x) $ xs)
unique _ = []
One question left: would the second definition be more efficient if written:
unique e = e
Inquiring minds want to know...
Dan
Dan Weston wrote:
Now that I mention it, the base case is much less often called than the
recursive case, so I would in hindsight flip the order of the two
(mutually exclusive) partial function definitions:
unique :: Eq a => [a] -> [a]
unique (x:xs) = x : (unique . filter (/= x) $ xs)
unique [] = []
This should be marginally more efficient. I doubt that GHC would
automatically detect that a) they are mutually exclusive and b) the
second is called less often than the first!
Dan
Dan Weston wrote:
>
Close. Actually, the author upstream (i.e. me) had in mind:
> uniq :: Eq a => [a] -> [a]
> uniq [] = []
> uniq (x:xs) = x : uniq (filter (/= x) xs)
_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe
