One option could be something like:
data Z
data S n
data Vec n a where
Nil :: Vec Z a
Cons :: a -> Vec n a -> Vec (S n) a
data Length n where
One :: Length (S Z)
Two :: Length (S (S Z))
Seventeen :: Length (S (S (S (S (S (S (S (S (S (S (S (S (S (S (S (S (S
Z)))))))))))))))))
data FixedVec a where
FixedVec :: Legnth n -> Vec n a -> FixedVec a
But it's obviously rather cumbersome :)
On Wed, Oct 13, 2010 at 7:57 AM, Jason Dusek
Is there a way to write a Haskell data structure that is necessarily only one or two or seventeen items long; but that is nonetheless statically guaranteed to be of finite length?
-- Jason Dusek Linux User #510144 | http://counter.li.org/ _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe