>> A macro that wants to put identifiers in a binding position MUST produce the
>> whole binding form for those identifiers.
>
> Well, that's pretty much what match expanders are. Although the `match` forms
> have to recognize these match expanders specially, and expand them itself,
> one step at a time.
That's why I think of `match` as special: it has its own means of extending its
interface, namely with match expanders.
What I'm curious about is the more general situation of composing macros that
hold identifiers.
> I was about to try to apply its awesome power to your example, but I just
> realized that in your new example, the s-expression `(id-maker a ZIM b ZAM
> c)` isn't actually used in a binding position. Instead the individual ids
> within it are used in binding positions.
Perhaps I'm misusing the term "binding position". I understand it as "the place
where the identifiers sit so they'll get bound". So x and y are in binding
positions here:
(define x 42)
(let ([y 42])
y)
And in my sample binding macro:
(define-syntax-rule (binding-form _topid (_id ...))
(define (_topid)
(let ([_id '_id] ...)
(displayln (format "~a bound ~a" '_topid _id)) ...)))
whatever `(id ...)`s are in the second argument will be bound (within `let`) so
the second argument position is impliedly a binding position. Wrong?
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