> Or am I wrong? Is it somehow possible
> to implement ConstantPoint in
> Smalltalk?

If you need a point that do not move,
 do not send #move messages to the point.
Nothing more efficient than the action
 that has not been done.
(if you have points that move and points that
 do not move... it is very provable to have a
 "failure" or a wrong point in the wrong place)

best,
Ale.



----- Original Message ----- 
From: "Matej Kosik" <kosik at fiit.stuba.sk>
To: "The general-purpose Squeak developers list"
<squeak-dev at lists.squeakfoundation.org>
Sent: Thursday, October 19, 2006 4:28 AM
Subject: Re: Retrofitting objcaps


> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi Michael
>
> Michael van der Gulik wrote:
> >
> >
> > On 18 Oct 2006 19:36:02 -0400, *Lex Spoon* <lex at cc.gatech.edu
> > <mailto:lex at cc.gatech.edu>> wrote:
> >
> >     Perhaps we should go all the way, though, and explore nested
classes.
> >     The only issue there is that it is a major change.  Implementing it
in
> >     the language is not a big deal, but updating all the browsers and
> >     debuggers and so on looks like a lot of work, especially if you try
to
> >     achieve anything like Smalltalk's level of tool quality.  Still,
maybe
> >     you have to go this far if you want to take the hard line on lexical
> >     scope and get a usable, security-sensible system.
> >
> >
> > Nested classes? What do you mean? Are you talking about nested
> > Namespaces (org.squeak.kernel.numbers.SmallInteger)?
> >
>
> Have you read papers about E? Have you read Mark Miller's dissertation?
> http://www.erights.org/talks/thesis/index.html
>
> "Nested classes", "nested functions" or lexical scoping is related to
> the unusual (like in lambda-calculus, like in pi-calculus, etc) rules
> which determine which variable names are visible in the particular point
> in the source code. It may seem "weird" but it is one mechanism which
> can be used to build secure language (in the sense of E).
>
> Can we implement Point in Smalltalk and E? Yes.
>
> What about ConstantPoint? Constant point is such an object which behaves
> exactly like a Point except for that it cannot be moved (once it is
> created). Can we implement such a thing in Smalltalk? Yes, it is
> "enough" to implement E interpreter in Squeak and then you are done. Can
> we implement constant point directly in E? Yes, it is trivial (few lines
> of code).
>
> Or am I wrong? Is it somehow possible to implement ConstantPoint in
> Smalltalk?
> - --
> Matej Ko?ík
> icq: 300133844, skype: matej_kosik, sarkan at jabber.sk
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.2.2 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org
>
> iD8DBQFFNykgL+CaXfJI/hgRAs3NAKDDbxKxZpJ+3TUGrgDrxNMZkHiDAACggP4s
> l5V8WAp1Yf8Wzy6FOuxSfm4=
> =CQjN
> -----END PGP SIGNATURE-----
>