Re: macros / code construction (and assignment)

[David.Ungar@Eng.Sun.COM (David Ungar)]

Good stuff, Brook--!

Rainer, I'll try to explain my viewpoint one last time:

I believe that whether or not you like macros depends a lot
on your background and expectations.

If you are mathematically grounded and inclined, you may
see computer programs as rewriting systems sort of like proofs.
There is a whole tradition in CS, starting with (pure) Lisp that
springs from this well, and it has contributed a lot.
Macros fit in fine here, just another way to do rewriting.
It's fine with me for suitably inclined, educated, and abled
folks to take this viewpoint, but I (and in my opinion
many others) are unable to.

If you come from physics, or your early exposure was to interpreted languages
like APL, or ST, you are likely to feel that working with a computer
is about the direct & immediate manipulation of stuff--objects, matrices, etc--
and macros seem silly. After all, the base language already lets me
extend the behavior of the computer, adding a second step,
another execution model, just complicates things. In this school,
you hope that the syntax is bearable enough not to need extension--
after all English speakers manage pretty well with those 26 letters--
and you try to build extensible semantics in the language.
(Blocks are a great example here.) You also try to build
an implementation that supports this.
With our implementation
the sort of "if: bool Then: b1 Else: b2" method runs as fast as
a macro--in fact we beat Lisps in benchmarks.
So, you trade off simplicity of language and execution model
against some amount of low-level extensisibilty and complexity in the
implementation.
That's why Self is as it is (IMHO)--Randy will have a different view.

As far as assignment is concerned--I am more interested in building
things with objects than inside of them. But my favorite treatment
of this area may well be Glyphic's, by Mark Leczner (sp?).
Again, my values are simplicity and explainability. I don't give a
fig for expressive power beyond what Self already has.
I have even toyed with reducing Self a bit--but all these types of
arguments generally bottom out on assumptions about how frequently
certain kinds of programs will be written, and that is very, very
subjective. Personally, I listen to (in no particular order)
Randy, Peter, Mario, and of course, Ole Madsen (and others--
please don't feel bad if I forgot to include you)
I feel that I share their values and trust their clarity of vision.
Ole in particular has had many many years of experience
(himself and through working with his colleagues)
in OO stuff, and the Beta (and I guess Simula)
folks seem to have more experience
in the statically-typed OO area than anybody.

Rainer, I will leave you with one last thought--
my worst mistakes have always resulted from
being too clever.

- Dave

-- Dave