Re: [Haskell] Re: Fixed-length vectors in Haskell, Part 2: Using no extensions

[Daan Leijen]

Ashley Yakeley wrote: In article <[EMAIL PROTECTED]>, David Menendez <[EMAIL PROTECTED]> wrote: data Vec 0 a = Nil data Vec s v a = Cons a (v a) Some aliases for convenience: type Vec 1 = Vec s Vec 0 type Vec 2 = Vec s Vec 1 type Vec 3 = Vec s Vec 2 type Vec 4 = Vec s Vec 3 I don't understand this at all, and neither does GHC. You seem to have lost the underscores :-) It can be written without underscores as:  data Vec0 a = Nil  data VecS v a = Cons a (v a)  type Vec1 = VecS Vec0  type Vec2 = VecS Vec1 All the best,  Daan Leijen Btw. David: nice example of useful GADT use!

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