Re: [Haskell] simulating dependent types; ghc/ghci discrepancy

data Show' = forall a . Show a => Show' a

The "forall a. Show a =>" context here has no effect on the representation; it merely constrains applications of the data constructor Show'. Since you have to say

print' :: Show' -> IO ()

anyway (thus providing the dictionary) there is no point in storing it. Thus

*DepTest> :t x x :: forall a. a

is indeed the type of x. There was a thread about this in the café recently; see http://www.haskell.org//pipermail/haskell-cafe/2004-March/005985.html http://www.haskell.org//pipermail/haskell-cafe/2004-March/005999.html http://www.haskell.org//pipermail/haskell-cafe/2004-March/005998.html --KW 8-)