> Nice, but how about a list destructor I'm not sure what you mean by destructor, if you mean an eliminator for case analysis then you can make a function
finite :: b -> (a -> Finite s1 a -> b) -> Finite s2 a -> b finite b _ (Finite []) = b finite _ f (Finite (x:xs)) = f x xs If you men functions that possibly remove elements from lists, then you can add definitions like these to the module: filter = onList . Prelude.filter tail = onList Prelude.tail onList :: ([a] -> [b]) -> Finite s a -> Finite s b onList f = Finite . f . infinite Don't export onList though! filter and map should be enough to define any list function you want outside the module. Note that the size-type doesn't correspond exactly to the size of the list, but that's not really a problem as long as you only want to guarantee finiteness. /J On 13 October 2010 16:41, Stephen Tetley <stephen.tet...@gmail.com> wrote: > Hi Jonas > > Nice, but how about a list destructor? > > ;-) > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe@haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >
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