>> On Apr 25, 2016, at 3:43 PM, Matthew Butterick <[email protected]> wrote:
>> ;;;;;;;;;;;;;;
>> #lang racket
>>
>> (define-syntax-rule (binding-form _topid (_id ...))
>> (define (_topid)
>> (let ([_id '_id] ...)
>> (displayln (format "~a bound ~a" '_topid _id)) ...)))
>>
>> (binding-form foo (a b c))
>> (foo) ; works
>>
>> (define-syntax-rule (id-maker _a "," _b "," _c)
>> (_a _b _c))
>>
>> (binding-form bar (id-maker a ZIM b ZAM c))
>> (bar) ; fails, will treat `(id-maker ..)` expr as list of literal ids
Actually, no need for match expanders or generic bind (it wasn't a binding
position anyway), this works:
#lang racket
(require syntax/parse/define)
(define-syntax-parser binding-form
[(binding-form _topid id-stuff)
#:with [_id ...] (local-expand #'id-stuff 'expression #f)
#'(define (_topid)
(let ([_id '_id] ...)
(displayln (format "~a bound ~a" '_topid _id)) ...
(void)))])
(binding-form foo (a b c))
(foo) ; works, prints foo found a, etc.
;; this has to be define-simple-macro, not define-syntax-rule
(define-simple-macro (id-maker _a "," _b "," _c)
(_a _b _c))
(binding-form bar (id-maker x "," y "," z))
(bar) ; works, prints bar found x, etc.
Actually I'm surprised that this worked; I expected it to be much more
difficult. Does this allow you to do what you want?
Alex Knauth
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