Am 16.01.2013 23:48, schrieb Lemol Morais Lutonda:

You realy need a generic indtype? what if to define it just as a Int?

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You are right that I don't need a generic indtype in the instance declarations, the following would be sufficient for me:

instance Sliceable (UArray Int Double) Int Double where (!) = (AU.!)

instance Sliceable (UArray Int Double) [Int] (UArray Int Double) where (!) arr ilist = listArray (0,end_ind) [(AU.!) arr i | i <- ilist] where end_ind = length ilist - 1

But also for this case a type annotation is necessary as in my original post. And within the class definition I think I need a generic indtype, because I want to be able to use arguments of type Int as well as [Int] as the second argument of (!).