Re: Why would anyone want opacity?

[Matthias Blume <blume@CS.Princeton.EDU>]

From: "Guillermo J. Rozas" <gjr@martigny.ai.mit.edu>
Subject: Re: Why would anyone want opacity?
Date: Tue, 30 Apr 96 16:36:34 -0400

> Interesting, but you probably consider young kids who are interested
> in how their radios/CDs/cars/computers work, and learn to probe them
> and improve them, quite imaginative and would encourage them.

Well, no.  Not always.  For example if they start taking the
fire-crackers apart that you can buy everywhere in Germany around New
Years Day.

There are excellent teaching kits, which tell the kid much more about
how a radio works -- because they come with the "source code", so to
speak.

> The various MIT Scheme compilers get rid of variables, choose frame
> formats and layouts, etc. with relative impunity.  They just leave
> "debugging" information behind that is accessed by the
> meta-programming facilities to make it appear to their user that
> nothing had happened, or to tell him/her that the naive model is
> broken (e.g. mutability of variables).
> 
> Yes, this means more work and a more complex model for the user of the
> meta-programming facilities, but so what?  Your alternative is not to
> provide them at all.

I think this is a matter of trade-off.  First we must ask what we gain
from doing the extra work and providing the facilities.  If we think
(and I do think) the gain is not worth the effort, then we might not
want to do the extra work.

-Matthias