[Haskell-cafe] snd and tuples of various sizes...
moonlite at dtek.chalmers.se
Fri Feb 2 07:28:49 EST 2007
On Thu, 2007-02-01 at 21:01 -1000, Tim Newsham wrote:
> instance Second [a] a where
> snd  = error "don't got none"
> snd (x:y:xs) = y
Would'nt that instance mean this:
snd  produces error
snd [x] gives 
I'd implement it something like this (if this works?):
instance Second [a] (Maybe a) where
snd  = Nothing
snd [x] = Nothing
snd (x:y:xs) = Just y
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