Question aboutthe use of an inner forall

[Scott J.]

Still some question: Ok a is a type  and Integer is a type . But a can be
instantiated to integer. This comes pretty close to call a therefore a type
variable.

Regards

Scott

----- Original Message ----- 
From: "Jon Cast" <jcast@ou.edu>
To: "Scott J." <jscott@planetinternet.be>
Cc: "Ashley Yakeley" <ashley@semantic.org>; <haskell-cafe@haskell.org>
Sent: Monday, August 19, 2002 3:48 AM
Subject: Re: Question aboutthe use of an inner forall


> "Scott J." <jscott@planetinternet.be> wrote:
> > A question: s is not a type variable as a isn't it? I mean a can be
> > of type Integer while s cannot.
> 
> Guessing at your question:
> 
> a has no type (and neither does s); it /is/ a type.  In Haskell, types
> have kinds.  And, both a and s have kind *.
> 
> Now then, the user can instantiate a to Integer, yes.  And the user
> cannot instantiate s to anything---that's what the `forall' is for.
> runST will (theoretically) instantiate s to something.  That could be
> Integer if the language implementors felt like it.  The user of runST
> certainly has to be prepared for the possibility.
> 
> Does that come close to answering your question?
> 
> > Regards,
> 
> > Scott
> 
> Jon Cast
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>