[Haskell-cafe] number-parameterized types and heterogeneous lists

[Harald ROTTER]

Hello,

sorry for the late answer, I was off for the weekend :-)

The paper "Number-parameterized types" by Oleg Kielyov is located at

      http://okmij.org/ftp/papers/number-parameterized-types.pdf

It impressively shows what one can do with Haskell's type system.
What I am after is the replacement of a "chain" of digits, like e.g.
      D1 $ D0 $ D0 $ Sz
by a list
      [D1,D0,D0]
so I can effectively use list operations on those "typed numbers". I also
wonder if there is some kind of
"generalized" foldr such that, e.g.
      D1 $ D0 $ D0 $ Sz = specialFoldr ($) Sz [D1,D0,D0]
I think that this foldr must be some "special" foldr that augments the data
type of the result in each foldr step.
Would this be possible or am I just chasing phantoms ?

Thanks

Harald.



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