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Re: the number of fields



On Sun, 7 Nov 2004 campbell@xxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:

It is because the implementation performs such heavy syntax-rules-based
computation that Scheme48's heap overflows.  You can 'fix' the problem
by increasing the heap, but that will solve it only temporarily.  The
real problem is that this SRFI's reference implementation just does too
much with syntax-rules;

I agree that it is a little silly to try to do so much with syntax-rules. Actually, early versions without inheritance were much simpler and very suitable for syntax-rules, and when it grew it took less energy each time to add a feature than to convert to a low-level macro system for which I would have to maintain a separate version for each Scheme I want to test it on (although I do have a partially converted but horrid-looking and verbose syntax-case version).

Also, if one version was to be posted as proof of concept, choosing syntax-rules was probably not entirely a bad decision. If I had done it in a low-level system, I would have probably chosen define-macro or syntax-case, in which case it would not have run on Scheme48 at all without some porting.

even if it doesn't overflow the heap or so
something equally horrid in other Scheme systems, it is _miserably_
sluggish.  I haven't used it much, but I've heard from some people that
it takes up to an hour to expand a single DEFINE-RECORD-TYPE form.

One could argue that those systems are not /usefully/ R5RS compliant. There is really no excuse for that kind of performance. On Petite Chez, which is interpreted, expansion is instantaneous. Even on MzScheme, which I regard as relatively slow, it takes of the order of only a second per record type definition on my modest machine.

It
would be a *gargantuan* improvement to provide at least two or three
reference implementations: the original one in plain syntax-rules, one
in syntactic closures (as the most simply expressive, I argue, hygienic
macro system -- the best basis for a _reference_ implementation), and
perhaps one or two in any number of the incompatible variants of
syntax-case.

I completely agree. Any volunteers? The soon-to-appear updated version is a little simpler and may be easier to convert. In the meantime I can send it privately to anyone upon request. It should also not be hard to write a low-level implementation from scratch.

Regards
Andre