On 7 Jun 2021, at 18:07, Marc Nieper-Wißkirchen <xxxxxx@nieper-wisskirchen.de> wrote:

>> One thing I'm already aware of: in the conclusion, I mention that it would be nice to have compiler macros in Scheme; at the time, I was unaware that R6RS Schemes effectively have them through the ability to have syntax patterns match an identifier out of first-position context, and that this is on the ballot for R7RS as part of syntax-case. One thing I'd like to know, not only in this context, is what (potential) implementers of R7 think of this: Do you think you could implement it?
>
> As someone who has implemented this kind of thing more than once: Adding identifier macros to existing macro systems is easy. So it is not a question of whether this can be technically done. The question is whether implementers are willing to implement it. Unfortunately, a lot of FUD was raised about it during the finalization of R6RS, so the topic seems a bit poisoned.

To my knowledge, though, you've mostly worked on new Scheme systems? (Correct me if my assumption is wrong.) I'm more concerned about systems like Chicken and Gambit with tens of thousands of lines of implementation code and goodness knows where in all those lines the assumption may be hiding that macros are only expanded from lists where the name of the macro is in first position and not from arbitrary identifiers anywhere. There are also scoping issues which may conflict with existing implementations' need: if I have defined foo as identifier syntax, (let ((foo 'example)) foo) should still return example, which might break existing Schemes' assumptions about how namespacing of syntax keywords vs normal identifiers works.

But this whole area of Scheme is new to me, so maybe I'm just unintentionally spreading more FUD.

> It is probably a good idea to resolve this question first because the answer to it (and to the question of whether R7RS-large will have procedural macros) dictates what keyword and optional parameter proposals can be made work. The more syntactic abstractions we can use, the less we have to worry about performance and usability.

Yes, I've come to agree with this myself. Fortunately it won't be so long until we know, I think John is intending to ballot the question later this year or early next, since that docket is nearly completely SRFI’d already.

Daphne