Re: Why would anyone want opacity?

[Guillermo J. Rozas <gjr@martigny.ai.mit.edu>]

|   Date: Tue, 30 Apr 1996 17:04:47 -0400
|   From: Matthias Blume <blume@CS.Princeton.EDU>
|
|   > 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.

So you don't believe in debugging?  The point that I believe you've
missed is that the _same_ information that is left behind for
debugging can be used by _other_ meta-programming tools.  In fact,
once you make that observation, you realize that the debugger is
_nothing special_.  Users can write their own if they so wish.

Thus saying that the extra work is not worth it is essentially saying
that debugging is not worth it, and I doubt you believe that.