On Wed, Apr 14, 2004 at 06:29:38PM +0200, Tomasz Zielonka wrote:
Is it possible to unwrap an existential type in ghci?
For me this seems to be a bug in GHCi. I wonder if there a type in Haskell-with-extensions that could be assigned to x?
Probably GHCi could do the same as in this situation and report an error: *Exist> do Show' y <- return (Show' "QWrwer"); return y <interactive>:1: Inferred type is less polymorphic than expected Quantified type variable `a' escapes When checking an existential match that binds y :: a The pattern(s) have type(s): Show' The body has type: m a In a 'do' expression: Show' y <- return (Show' "QWrwer") In the definition of `it': it = do Show' y <- return (Show' "QWrwer") return y Best regards, Tom -- .signature: Too many levels of symbolic links