match questions

[Kent M Pitman <KMP@STONY-BROOK.SCRC.Symbolics.COM>]

When you say you think we want a matcher, does the "we" refer to Scheme
designers or to Scheme users?

In my experience, users want virtually anything that will save them
work.  So any user who's got a matching problem would want a matcher.
Of course, users get to wipe clean their assumptions every time they
start over on a new project so they tend to have a more short-sighted
view of things.

On the other hand, a language designer is pretty much stuck with
anything he puts in his language forever after. For that reason, he must
be more particular.

If you're thinking of adding a match facility to Scheme, you must first
decide at what level you were going to add it.

If you add it as linguistic glue (as, for example, in Prolog), you have
a lot of work ahead of you figuring out how to weave it into the fabric
of the language so that it doesn't end up feeling hastily tacked on.

If you just want to add a tool that isn't integrated at the glue level,
you should be ready to justify why you chose to add that tool and not
the myriad of other possible tools that Common Lisp and company have
adopted while Scheme has steadfastly shunned as contrary to the goals of
a simple and elegant language.

By the way, Jonathan has convinced me that a graceful matcher is
possible so I'm not trying to talk you completely out of it. I just
think there's no good argument for it being anywhere but in the Yellow
Pages unless you're willing to go the extra mile and make the language
really use it at a very low level... and I don't see anyone going that
extra mile (nor do I expect that if they did the others would accept it).