[racket-users] Macro generating macro question

[Kevin Forchione]

Hi guys,
I’m stumped. In a nutshell I want to write a macro that is passed an id and will produce a macro called id that can take variable arguments. I’m sure I’m overlooking something fundamental. The basic form below “works” if I don’t have ellipsis aver the variables, but that’s not what I’m after. Here’s an example that is obviously wrong, but is along the lines of what I’m looking for:

#lang racket


(require (for-syntax syntax/parse
racket/syntax))

(define-syntax (make-id-macro stx)
(syntax-parse stx
[(_ id)
(with-syntax ([name (format-id #'id "do-~a" #'id)])
#'(define-syntax (name stx)
(syntax-parse stx
[(_ parms ...)
#'( list parms ...)])))]))

Any help in this and explaining why it fails would be greatly appreciated.

-Kevin

[Stephen De Gabrielle]

Hi Kevin 

The most active places for ‘Racketeers’ is the Racket [Discourse](https://racket.discourse.group/) and [Discord](https://discord.gg/6Zq8sH5) 

Please join us!

See also https://github.com/racket/racket/wiki/Macros - in particular i think you may find what you are looking for in 

https://docs.racket-lang.org/syntax-parse-example/index.html

(many who prefer email just use discourse in ‘mailing list mode’)

Best regards

Stephen

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----

[Jens Axel Søgaard]

Hi Kevin,

When you are writing macro generating macros there are two levels of ellipsis.
The outer one, which you can write as ... as normal and the inner one which you need to escape. 
You can escape it with (... ...). That looks odd to me, so I usually bind it to an identifier named ooo.

#lang racket
(require (for-syntax syntax/parse
                     racket/syntax))

(define-syntax (make-id-macro stx)
  (syntax-parse stx
    [(_ id)
     (with-syntax ([name (format-id #'id "do-~a" #'id)]

                   [ooo  #'(... ...)])

       #'(define-syntax (name stx)
           (syntax-parse stx

             [(_ parms ooo)
              #'(list parms ooo)])))]))

(make-id-macro foo)
(do-foo 1 2)


See you on Racket Discourse.
/Jens Axel

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--
Jens Axel Søgaard

[Kevin Forchione]

On May 24, 2023, at 2:11 AM, Jens Axel Søgaard <jens...@soegaard.net> wrote:

#lang racket
(require (for-syntax syntax/parse
                     racket/syntax))

(define-syntax (make-id-macro stx)
  (syntax-parse stx
    [(_ id)
     (with-syntax ([name (format-id #'id "do-~a" #'id)]
                   [ooo  #'(... ...)])
       #'(define-syntax (name stx)
           (syntax-parse stx
             [(_ parms ooo)
              #'(list parms ooo)])))]))

(make-id-macro foo)
(do-foo 1 2)

Thanks! That was the fundamental concept I was missing. I don’t recall seeing that in the documentation, but now that I know I’ll search for that and see if I glossed over it somehow. 

-Kevin