Why not be dependently typed?

Question

I have seen several sources echo the opinion that \"Haskell is gradually becoming a dependently-typed language\". The implication seems to be that with more and more languag

Answer 1

John that's another common misconception about dependent types: that they don't work when data is only available at run-time. Here's how you can do the getLine example:

data Some :: (k -> *) -> * where
  Like :: p x -> Some p

fromInt :: Int -> Some Natty
fromInt 0 = Like Zy
fromInt n = case fromInt (n - 1) of
  Like n -> Like (Sy n)

withZeroes :: (forall n. Vec n Int -> IO a) -> IO a
withZeroes k = do
  Like n <- fmap (fromInt . read) getLine
  k (vReplicate n 0)

*Main> withZeroes print
5
VCons 0 (VCons 0 (VCons 0 (VCons 0 (VCons 0 VNil))))

Edit: Hm, that was supposed to be a comment to pigworker's answer. I clearly fail at SO.