Question aboutthe use of an inner forall
Scott J.
jscott@planetinternet.be
Mon, 19 Aug 2002 03:19:13 +0200
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A question: s is not a type variable as a isn't it? I mean a can be of =
type Integer while s cannot.
Regards,
Scott
----- Original Message -----=20
From: "Ashley Yakeley" <ashley@semantic.org>
To: "Scott J." <jscott@planetinternet.be>; "Haskell Cafe List" =
<haskell-cafe@haskell.org>
Sent: Saturday, August 17, 2002 6:15 AM
Subject: Re: Question aboutthe use of an inner forall
> At 2002-08-16 20:57, Scott J. wrote:
>=20
> >However what for heaven's sake should I think of
> >
> >runST :: forall a ( forall s ST s a) -> a ?
>=20
> runST :: forall a. ((forall s. ST s a) -> a)
>=20
> "For all a, if (for all s, (ST s a)) then a."
>=20
> You may apply runST to anything with a type of the form (forall s. ST =
s=20
> a), for any 'a'.
>=20
>=20
> --=20
> Ashley Yakeley, Seattle WA
>=20
> _______________________________________________
> Haskell-Cafe mailing list
> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
>=20
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<DIV><FONT face=3DArial size=3D2>A <STRONG>question</STRONG>: =
<STRONG>s</STRONG> is=20
not a type variable as <STRONG>a</STRONG> isn't it? I mean =
<STRONG>a</STRONG>=20
can be of type Integer while <STRONG>s</STRONG> cannot.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Regards,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Scott</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>----- Original Message ----- </FONT>
<DIV><FONT face=3DArial size=3D2>From: "Ashley Yakeley" <</FONT><A=20
href=3D"mailto:ashley@semantic.org"><FONT face=3DArial=20
size=3D2>ashley@semantic.org</FONT></A><FONT face=3DArial =
size=3D2>></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>To: "Scott J." <</FONT><A=20
href=3D"mailto:jscott@planetinternet.be"><FONT face=3DArial=20
size=3D2>jscott@planetinternet.be</FONT></A><FONT face=3DArial =
size=3D2>>; "Haskell=20
Cafe List" <</FONT><A href=3D"mailto:haskell-cafe@haskell.org"><FONT =
face=3DArial=20
size=3D2>haskell-cafe@haskell.org</FONT></A><FONT face=3DArial=20
size=3D2>></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Sent: Saturday, August 17, 2002 6:15=20
AM</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Subject: Re: Question aboutthe use of =
an inner=20
forall</FONT></DIV></DIV>
<DIV><FONT face=3DArial><BR><FONT size=3D2></FONT></FONT></DIV><FONT =
face=3DArial=20
size=3D2>> At 2002-08-16 20:57, Scott J. wrote:<BR>> <BR>> =
>However=20
what for heaven's sake should I think of<BR>> ><BR>> >runST =
::=20
forall a ( forall s ST s a) -> a ?<BR>> <BR>> runST :: =
forall a.=20
((forall s. ST s a) -> a)<BR>> <BR>> "For all a, if (for all s, =
(ST s=20
a)) then a."<BR>> <BR>> You may apply runST to anything with a =
type of the=20
form (forall s. ST s <BR>> a), for any 'a'.<BR>> <BR>> <BR>> =
--=20
<BR>> Ashley Yakeley, Seattle WA<BR>> <BR>>=20
_______________________________________________<BR>> Haskell-Cafe =
mailing=20
list<BR>> </FONT><A href=3D"mailto:Haskell-Cafe@haskell.org"><FONT =
face=3DArial=20
size=3D2>Haskell-Cafe@haskell.org</FONT></A><BR><FONT face=3DArial =
size=3D2>>=20
</FONT><A =
href=3D"http://www.haskell.org/mailman/listinfo/haskell-cafe"><FONT=20
face=3DArial=20
size=3D2>http://www.haskell.org/mailman/listinfo/haskell-cafe</FONT></A><=
BR><FONT=20
face=3DArial size=3D2>> </FONT></BODY></HTML>
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