[Haskell] simulating dependent types; ghc/ghci discrepancy

[Keith Wansbrough]

> 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-)