[Haskell] simulating dependent types; ghc/ghci discrepancy
Keith.Wansbrough at cl.cam.ac.uk
Wed Apr 14 17:58:55 EDT 2004
> 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.
> *DepTest> :t x
> x :: forall a. a
is indeed the type of x.
There was a thread about this in the café recently; see
More information about the Haskell