Define-attributes macro, is this useful, ideas for improvements?

Questions & Answers
5

Like @benknoble suggested I tried to rewrite the macro using more pattern matching, at first that seemed a bit difficult. But by using a helper macro, fixing my syntax-class (so that it keeps the original identifiers in #:with to ...) and using format-id like @SamPhillips suggested, I managed to get it quite conscise and now it shows arrows properly. Here is the new version:

#lang racket

(provide define-attributes)

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

(begin-for-syntax
  (define-syntax-class name-mapping
    #:description "name-mapping"
    [pattern from:id
             #:with to #'from]
    [pattern (from:id)
             #:with to '||]     ; empty symbol
    [pattern (from:id to-id:id)
             #:with to #'to-id]))

;(define-attributes (l r)    vec3- (x y z))  lx ly lz rx ry rz
;(define-attributes ([l])    vec3- (x y z))  x y z
;(define-attributes ([l o])  vec3- (x y z))  ox oy oz
;(define-attributes ([l l.]) vec3- (x y z))  l.x l.y l.z
;(define-attributes ([l])    vec3- (x y z [length len]))  x y z len
(define-syntax-parser define-attributes
  [(_ (ids:name-mapping ...+) prefix:id (attributes:name-mapping ...+))
   #`(begin (define-attributes-id #,this-syntax ids prefix attributes ...) ...)])

(define-syntax-parser define-attributes-id
  [(_ loc id:name-mapping prefix:id attribute:name-mapping)
   #:with newid    (syntax-property
                    (format-id #'id "~a~a" #'id.to #'attribute.to #:subs? #t)
                    'original-for-check-syntax #t)
   #:with accessor (format-id #'loc "~a~a" #'prefix #'attribute.from #:source #'loc)
   #:with expr     #'(accessor id.from)
   #'(define newid expr)]
  [(_ loc id:name-mapping prefix:id attributes:name-mapping ...+)
   #'(begin (define-attributes-id loc id prefix attributes) ...)])

;; example
(struct vec3 (x y z))

(define (x² x) (* x x))
(define (vec3-length v)
  (define-attributes ([v]) vec3- (x y z))
  (sqrt (+ (x² x) (x² y) (x² z))))

(define-syntax-rule (fmt x ...) (begin (displayln (~a (~a (quote x) ": " x "  ") ...))))

(module+ main
  (define l (vec3 3 5 7))
  (define r (vec3 0 2 4))

  (define-attributes (l r)    vec3- (x y z)) ; lx ly lz rx ry rz
  (define-attributes ([l])    vec3- (x y z)) ; x y z
  (define-attributes ([l o])  vec3- (x y z)) ; ox oy oz
  (define-attributes ([l l.]) vec3- (x y z)) ; l.x l.y l.z

  (fmt lx ly lz rx ry rz)
  (fmt x y z)
  (fmt ox oy oz)
  (fmt l.x l.y l.z)

  (let ()
    (define-attributes ([l])    vec3- (x y z [length len]))  ; x y z len
    (fmt x y z len)))

racket_attributes_3fps