On Oct 16, 2012, at 3:25 PM, Jon Rafkind wrote: > This is what syntax-parameters are for. > > (require racket/stxparam) > (define-syntax-parameter m (lambda (stx) (raise-syntax-error 'm "dont use > this outside deeper"))) > > (define-syntax-rule (deeper e) > (syntax-parameterize ([m (lambda (stx) #'1)]) > e)) > > (deeper (m)) -> 1
Okay, this makes sense; I'm just deeply freaked out (temporarily, I presume) that the syntax-parameterize occurs in the phase 0 code, and not the phase 1 code; rather than doing the transformation that I want to do during the evaluation of the macro, I'm embedding it in another macro, to be evaluated later. Sure! I'm okay with that. Um… I think. Thanks, John > > On 10/16/2012 04:18 PM, John Clements wrote: >> This seems like a straightforward question; apologies if I just haven't dug >> deep enough to find the answer. >> >> I want to define a macro whose meaning depends on its context. More >> specifically, I want to define an "outer" macro that gives a particular >> meaning to the "inner" macro. >> >> I can see how to get the job done in a yucky way, using mutation: >> >> #lang racket >> >> ;; I want m's meaning to depend on its context >> (define-syntax (m stx) >> #`#,(unbox the-box)) >> >> (define-syntax (deeper stx) >> (syntax-case stx () >> [(_ arg) >> ;; I want to change the meaning of m, here: >> (set-box! the-box 16) >> #'arg])) >> >> ;; yucky mutation-based way to get the job done >> (define-for-syntax the-box (box 13)) >> >> >> (deeper (m 134)) >> >> >> … but it seems like there must be a simple way for the outer binding to say >> "whatever meaning the inner macro wants it to have". >> >> Don't tell me, it's define-for-inner-syntax/local-expand. I just made that >> up, so I hope it's wrong :). >> >> John >> >> >> >> >> ____________________ >> Racket Users list: >> >> http://lists.racket-lang.org/users > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users
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