Fw: Question aboutthe use of an inner forall

[Scott J.]

Sorry there are two mailers on this machine
 Regards
SCott

----- Original Message -----
From: "Jan Brosius" <jscott@planetinternet.be>
To: "Jon Cast" <jcast@ou.edu>
Cc: <haskell-cafe@haskell.org>
Sent: Monday, August 19, 2002 4:15 AM
Subject: Fw: Question aboutthe use of an inner forall


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