Simple answer: you always have to have the single element first, then the list bit second. It's just the way it is. You can learn why later on ;-)
On 7/11/07, Alexteslin <[EMAIL PROTECTED]> wrote:
Oh, I am lost now - for now anyway. I am attempting to do next exercise in the book to define reverse function using primitive recursion and pattern matching on lists. But getting stack because when i con in front of xs (xs:x) i get en error, which i thought i would be getting anyway. I tried to define a helper function and cons there in front of xs and i get type errors again. I know these are easy and boring questions but i would appreciate a hint. Thank you Neil Mitchell wrote: > > Hi > >> unique = unique' [] >> >> unique' _ [] = [] >> unique' history (x:xs) = if x `elem` history >> then next >> else (x:next) where next = (uniq' (x:hist) xs) > > You can express this more neatly: > > unique' _ [] = [] > unique' history (x:xs) = [x | x `notElem` history] ++ unique' (x:history) > xs > > Thanks > > Neil > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > > -- View this message in context: http://www.nabble.com/function-unique-tf4058328.html#a11547781 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
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