[Haskell-cafe] Existencial quantification and polymorphic datatypes

2009-01-20 Thread Mauricio 

Hi,

I'm trying, without success, to understand the difference
between existencial quantification and polymorphic
datatypes. Can you give me a hint, or an example where
one is valid and the other is not?

Thanks,
Maurício

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Re: [Haskell-cafe] Existencial quantification and polymorphic datatypes

2009-01-20 Thread Lennart Augustsson 
Do you mean difference between
  data A a = A a
and
  data B = B a -- leaving out the forall
?

On Tue, Jan 20, 2009 at 10:02 AM, Mauricio briqueabra...@yahoo.com wrote:
 Hi,

 I'm trying, without success, to understand the difference
 between existencial quantification and polymorphic
 datatypes. Can you give me a hint, or an example where
 one is valid and the other is not?

 Thanks,
 Maurício

 ___
 Haskell-Cafe mailing list
 Haskell-Cafe@haskell.org
 http://www.haskell.org/mailman/listinfo/haskell-cafe

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