[R6RS] syntax-case semantics

[Michael Sperber]

William D Clinger <will at ccs.neu.edu> writes:

> I'm worried that this is the worst of all possible worlds.
> If we say syntax objects are not supposed to be taken apart
> except by syntax-specific taker-aparters, but allow systems
> to represent syntax objects as in SRFI 72, I think a lot of
> systems are likely to do that, and we're liable to end up
> with a portability problem: lots of SRFI-72-compliant macros
> that aren't R6RS-compliant.

I agree.

> I was kind of hoping someone would offer an argument for
> making syntax objects opaque that made sense from a user's
> or macro writer's perspective.  Almost all of the SRFI 72
> arguments for opaque syntax objects, and ours too, have
> been argued from an implementor's perspective, mostly on
> the source/object correlation.

I remember my first steps trying to use explicit-renaming macros, and
trying to understand the SYNTAX-CASE papers, and the fact that
compound syntax are lists there always confused me to no end as a
user.  This may be a presentation issue, and it might also be the same
kind of confusion as with QUOTE and QUASIQUOTE (that is, the kind that
goes aways once your brain cells have regrouped), but maybe it's a
data point.

I still find it, as a user, counterintuitive and ad-hoc to (to
formulate this in very naive terms) overlay datums upon syntax and
only selectively change those bits (the symbols/identifiers) that get
affected by the particular notion of hygiene we have, and thus
allowing annotation, and not do it for the rest.

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla