[racket] define-match-expander

The match pattern (? number? n) matches  number and
binds it to n.

   > (match 1 [(? number? n) n])
   1

I'd like to write  (match 1 [n:num n]) instead.

Since there is no define-identifier-match-expander I have
tried to make (match 1 [(n:num) n]) work. I need a hint.

Here is a non-working attempt:

(define-match-expander n:num
  (λ(stx)
    (syntax-case stx ()
      [(id)
       (with-syntax ([n (syntax/loc #'id n)])
         #'(? number? n))])))


(check-equal? (match 1 [(n:num) n]) 1)
(check-equal? (match 'x [(n:num) n] [_ 2]) 2)

/Jens Axel






--
Jens Axel Søgaard