Fw: Question aboutthe use of an inner forall

[Jan Brosius]

Still some question: Ok a is not a type  but Integer is a type . But a can
be
 instantiated to integer. This comes pretty close to call a therefore a type
 variable, Isn't it?

And otherwise why writing forall a etc.

Regards

Scott

----- Original Message -----
From: "Scott J." <jscott@planetinternet.be>
To: "Jon Cast" <jcast@ou.edu>
Cc: <haskell-cafe@haskell.org>
Sent: Monday, August 19, 2002 4:09 AM
Subject: Re: Question aboutthe use of an inner forall


> 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
> >
>
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