Re: difficulty of writing translators

["Perry E. Metzger" <perry@piermont.com>]

Jim Blandy writes:
> Yes, I'm opposed to adding variable tracing to Guile at the Scheme
> level.
> 
> People need to have some sense of which code could be run in response
> to a particular action; if setting a variable causes new font metrics
> to be downloaded (for example), or some other huge and complicated
> action, then that principle is kind of broken.

Well.... yes and no.

In Scheme, such an action would obviously violate the
language. However, in a purely object oriented language, there is no
reason you can't override the assignment or similar methods. In fact,
Smalltalk's Model-View-Controller GUI model (the best I know of!)
depends to a large extent on such sorts of overrides. If you update a
variable's value, something displaying that variable will
automagically update the GUI, which is extremely useful.

Of course, this is Scheme, not Smalltalk. Smalltalk has the notion of
an object controlling all its own access methods -- scheme does not.

Perry