[Haskell] simulating dependent types; ghc/ghci discrepancy

Tomasz Zielonka t.zielonka at students.mimuw.edu.pl
Wed Apr 14 19:24:01 EDT 2004


On Wed, Apr 14, 2004 at 04:58:55PM +0100, Keith Wansbrough wrote:
> > 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.

Aren't you talking about a different declaration?

  data Show a => Show' a = Show' a

Best regards,
Tom

-- 
.signature: Too many levels of symbolic links


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