On Tue, 10 Oct 2006 falseep@gmail.com wrote:
Hi all, I'm trying to implement a function that returns the shorter one of two given lists, something like shorter :: [a] -> [a] -> [a] such that shorter [1..10] [1..5] returns [1..5], and it's okay for shorter [1..5] [2..6] to return either.
Simple, right?
I am still very much of a newbie myself, so sorry for possibly un-haskellish style and all, but this seems to work for me: ===== data WhichOne = SelUnknown | SelLeft | SelRight shorter :: [a] -> [a] -> [a] shorter la lb = selectedof $ sorttuple (SelUnknown,la,lb) selectedof :: (WhichOne,[a],[a]) -> [a] selectedof (SelLeft,la,lb) = la selectedof (SelRight,la,lb) = lb selectedof (_,la,lb) = error "selectedof unselected tuple" sorttuple :: (WhichOne,[a],[a]) -> (WhichOne,[a],[a]) sorttuple (_,(a:xa),(b:xb)) = prefixt a b (sorttuple (SelUnknown,xa,xb)) sorttuple (_,[],[]) = (SelLeft,[],[]) sorttuple (_,(a:xa),[]) = (SelRight,(a:xa),[]) sorttuple (_,[],(b:xb)) = (SelLeft,[],(b:xb)) prefixt :: a -> a -> (WhichOne,[a],[a]) -> (WhichOne,[a],[a]) prefixt a b (w,la,lb) = (w,(a:la),(b:lb)) ===== What do you think? Eugene