match-expander-ex.rkt

#lang racket

(require (prefix-in r: racket))

(define-match-expander seq
  (λ (stx)
    (syntax-case stx ()
      [(_ p ...)
       #'(app sequence->list (list p ...))])))

(define-match-expander dict
  (λ (stx)
    (syntax-case stx ()
      [(_ #:only [pk pv] ...)
       #'(app dict->list (list (cons pk pv) ...))]
      [(_ [pk pv] ...)
       #'(app dict->list (list-no-order (cons pk pv) ... rst (... ...)))])))

(match (list (cons 1 2) (cons 2 3))
  [(dict [1 2] [2 4]) 'a]
  [(dict #:only [1 2]) 'b]
  [(dict #:only [1 2] [2 3]) 'c])

(match (hash 1 2 2 3)
  [(dict [1 2] [2 4]) 'a]
  [(dict #:only [1 2]) 'b]
  [(dict #:only [1 2] [2 3]) 'c])

(match (vector 7 2 4)
  [(dict [1 2] [2 4]) 'a]
  [(dict #:only [1 2]) 'b]
  [(dict #:only [1 2] [2 3]) 'c])

(match (list 1 2 3)
  [(seq 1 2 3) 'a])
(match (vector 1 2 3)
  [(seq 1 2 3) 'a])
(match (stream 1 2 3)
  [(seq 1 2 3) 'a])