RPG on Vectors versus Arrays

[Scott E. Fahlman <Fahlman at Cmu-20c>]

I'm sure each of us could design a better language than Common Lisp is
turning out to be, and that each of those languages would be different.
My taste is close to RPG's, I think: in general, I like primitives that
I can build with better than generalizations that I can specialize.
However, Common Lisp is politics, not art.  If we can come up with a
single language that we can all live with and use for real work, then we
will have accomplished a lot more than if we had individually gone off
an implemented N perfect Lisp systems.

When my grandchildren, if any, ask me why certain things turned out in
somewhat ugly ways, I will tell them that it is for the same reason that
slaves count as 3/5 of a person in the U.S. Constitution -- that is the
price you pay for keeping the South on board (or the North, depending).
A few such crocks are nothing to be ashamed of, as long as the language
is still something we all want to use.  Even with the recent spate of
ugly compromises, I think we're doing pretty well overall.

For the record, I too believe that Common Lisp would be a clearer and
more intuitive language if it provided a simple vector data type,
documented as such, and presented hairy multi-D arrays with fill
pointers and displacement as a kind of structure built out of these
vectors.  This is what we did in Spice Lisp, not to fit any particular
instruction set, but because it seemed obviously right, clear, and
easily maintainable.  I have always felt, and still feel, that the Lisp
Machine folks took a wrong turn very early when they decided to provide
a hairy array datatype as primary with simple vectors as a degenerate
case.

Well, we proposed that Common Lisp should uniformly do this our way,
with vectors as primary, and Symbolics refused to go along with this.  I
don't think this was an unreasonable refusal -- it would have required
an immense effort for them to convert, and most of them are now used to
their scheme and like it.  They have a big user community already,
unlike the rest of us.  So we have spent the last N months trying to
come up with a compromise whereby they could do things their way, we
could do things our way, and everything would still be portable and
non-confusing.

Unfortunately, these attempts to have it both ways led to all sorts of
confusing situations, and many of us gradually came to the conclusion
that, if we couldn't have things entirely our way, then doing things
pretty much the Lisp Machine way (with the addition of the simple-vector
hack) was the next best choice.  In my opinion, the current proposal is
slightly worse than making vectors primary, but not much worse, and it
is certainly something that I can live with.  The result in this case is
close to what Symbolics wanted all along, but I don't think this is the
result of any unreasonable political tactics on their part.  Of course,
if RPG is seriously unhappy with the current proposal, we will have to
try again.  There is always the possibility that the set of solutions
acceptable to RPG or to the S1 group does not intersect with the set
acceptable to Symbolics, and that a rift is inevitable, but let us hope
that it does not come down to that.

-- Scott