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Re: [Scheme-reports] [wg2] in support of single-arity procedural syntax transformers
On Wed, May 18, 2011 at 11:50 AM, Eli Barzilay <eli@x> wrote:
> (a) Right, but in the current context it's important to focus on
> *existing* systems, and non syntax case macro systems that have a
> single argument input are either non-existent or uncommon enough
> that I've never seen one.
It was a minor point - future compatibility is not completely irrelevant -
but we can drop it.
> (b) Without such a system to show otherwise, formalizing the current
> practice is a far better choice as far as a standard goes.
Unfortunately, current practices disagree.
> (c) Formalizing a system that *contradicts* R6RS is ... particularly
> silly. Regardless of R7RS being a derivative language or not
> being one. Even more so when practically the only argument that I
> see against accomodating both is some kind of non-technical
> "discrimination" argument. ("Non-technical" since it's easy to
> have both, or only one.)
No, you don't get to turn this around. It was R6RS that contradicted
reality - the reality that existing syntactic-closures implementations
simply can't support single argument expanders (modulo hypothetical
rewrites to their macro systems discussed in this thread).
WG1 is staying compatible with everything by limiting itself to
syntax-rules. WG2 is currently being conservative and sticking
to ER, which any reasonably powerful macro system can support.
Neither contradicts R6RS.
If WG2 does support syntax-case, then adding a wrapper is
trivial for existing syntax-case implementations, and makes it
easier for other implementations to support. It would encourage
more widespread syntax-case support.
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