[squeak-dev] Evolution from the primordial stew (was: The Trunk: System-dtl.609.mcz)

David T. Lewis lewis at mail.msen.com
Sat Oct 26 14:35:38 UTC 2013


On Sat, Oct 26, 2013 at 07:55:25AM +0000, H. Hirzel wrote:
> What is NextVariableCheckTime  used for? Is it that there is no active
> use of it anymore?
> 
> --Hannes

It was used a long time ago to schedule periodic checks of something.
I'm not sure what it was, but it may have been related to handling the
state of variables during copies to or from image segments.

The class DeepCopier is of course an object, and that object has been
in the image for a long time. By looking at that object, you could
see that it pointed to a value that happened to represent a time stamp,
and since that time stamp represented a time in 2001, it was a pretty
good clue as to when the variable had last been updated.

I was only pointing this out because it reminded me once again of how
different Squeak is from environments that think of everything as file
based source code, rather than as objects.

Dave

> 
> On 10/26/13, David T. Lewis <lewis at mail.msen.com> wrote:
> > On Fri, Oct 25, 2013 at 10:58:49PM +0000, commits at source.squeak.org wrote:
> >>
> >> Item was changed:
> >>   Object subclass: #DeepCopier
> >>   	instanceVariableNames: 'references uniClasses newUniClasses'
> >> + 	classVariableNames: ''
> >> - 	classVariableNames: 'NextVariableCheckTime'
> >>   	poolDictionaries: ''
> >>   	category: 'System-Object Storage'!
> >
> > One thing that I find rather appealing about Squeak is that its stew of
> > living objects contains things that have existed since before my time.
> > Even if the so-called "code" changes, the objects still can survive.
> >
> > Every once in a while this turns out to have some practical benefit. For
> > example, the class DeepCopier had a class variable that kept track of some
> > sort of time stamp (in the form of NextVariableCheckTime seconds). Some
> > time in an earlier millenium, a primeval user of the class had set this
> > variable, then wandered off into a tar pit. We do not really know who that
> > may have been, but the original object (class DeepCopier) has survived in
> > the image, and the last updated value of its NextVariableCheckTime has
> > remained undisturbed since those early days. Thus when I became curious
> > about whether this class variable was being used, I was able to look at
> > its value and convert it to a DateAndTime to see that it had not been
> > updated in the last dozen years or so.
> >
> > It's a small thing, but just try keeping track of that with a version
> > control system.
> >
> > Dave
> >
> >
> >


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