🚀 go-pugleaf

On 21 Aug 92 19:42:01 GMT, sm86+@andrew.cmu.edu (Stefan Monnier) said:

pcg> A system builder can create a complete list of all the types in an
pcg> application (unless they can be defined at run time), and can do
pcg> such overload resolution at system building time, statically. I
pcg> think a 'system building' tool is something that is quite useful in
pcg> general, especially if it can be used more or less incrementally.

sm86> Such a system builder is only useful in non-OO operating systems
sm86> or environments:

Ahhhh, capability OSes tend to be a big interest of mine...

sm86> In such OO-environments (like Smalltalk), each class is shared
sm86> among all applications (and even used by the system itself)

and I think we can do better here, even if I have seen nothing like what
I am going to describe.

A lot of optimization can be done only by more or less early reduction;
for example, the system builder reduces statically the overloading info
for an entire application. You are right that in traditional OO
environments this cannot be done, but this is only because it is assumed
that the entire application can be modified after system building:

sm86> which means that you can't adapt a class to a particular situation
sm86> as it is dynamically used and loaded.

More precisely use and load don't give problems, it's modification that
might cause problems.

It might be entirely possible, combining ideas from Reid's versioning
and Bishop's ORSLA and Baker's collector and Hewitt's variation of it,
to have the system builder generate systems from 'frozen' originals or
sources, and maintain dependency links. If the originals are modified, a
new version is generated, and the system builder reruns and produces a
new version of the reduced/optimized application.

Clients active at the time the new version is created just ignore it.

I think that something like this is actually needed to support *mutable
typing* systems, in which it is possible to change data formats at run
time.

--
Piercarlo Grandi                   | JNET: pcg@uk.ac.aber
Dept of CS, University of Wales    | UUCP: ...!mcsun!ukc!aber-cs!pcg
Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@aber.ac.uk