There are positions that macros can’t operate. https://lexi-lambda.github.io/blog/2018/10/06/macroexpand-anywhere-with-local-apply-transformer/ explains this issue really well, so I recommend you to read it.
There’s also another issue, which is that you want
write-proc to be named
write-proc, but Racket, which has a hygienic macro system, will “rename” it automatically for you. So you need to explicitly indicate that you want the name
write-proc. Like this:
#lang racket (require racket/struct) (define-syntax (print-as stx) (syntax-case stx () [(_ lam1 lam2) #`(define #,(datum->syntax stx 'write-proc) (make-constructor-style-printer lam1 lam2))])) (struct point (x y) #:methods gen:custom-write [(print-as (lambda (obj) 'p) (lambda (obj) (list [point-x obj] [point-y obj])))]) (point 1 2)
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