Doing exercises from "Haskell tutorial" ...

Frank Atanassow [email protected]
Tue, 2 Oct 2001 17:52:29 +0200


Dmitry Astapov wrote (on 02-10-01 15:16 +0300):
>     union (SL []) (SL ys) = SL ys
>     union (SL (x:xs)) (SL ys) | member x (SL ys) = union (SL xs) (SL (x:ys))
>                               | otherwise        = union (SL xs) (SL ys)

I take it back: your implementation has a small problem in it, but nothing to
do with the Eq class. The two cases in the second clause for union should be
switched:

>     union (SL (x:xs)) (SL ys) | member x (SL ys) = union (SL xs) (SL ys)
>                               | otherwise        = union (SL xs) (SL (x:ys))

-- 
Frank Atanassow, Information & Computing Sciences, Utrecht University
Padualaan 14, PO Box 80.089, 3508 TB Utrecht, Netherlands
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