chezscheme-match

Pattern matching in Chez Scheme

---

library (match)

syntax match

Examples

Wildcard matching

(match (list 1 2 3)
  [_ 123])
; 123

Pair deconstruction

(match '(4 . 5)
  [`(,x . ,y) (+ x y)])
; 9

List deconstruction

(match (list 1 2 3)
  [`(,x ,@xs) x])
; 1

(match (list 1 2 3)
  [`(,x ,@xs) xs])
; (2 3)

(match (list 1 2 3)
  [`(,x ,@xs) xs])
; (2 3)

View patterns

(match 7
  [(x (add1 x) y) (cons x y)])
; (7 . 8)

(match (list 1 2 3 4)
  [`(2 ,@_)                  'huey]
  [(x (even? (length x)) #t) 'dewey]
  [`(,_ ,(x (even? x) #t))   'louie])
; dewey

💡 View patterns can be used to deconstruct types that are not natively supported like record types and hash tables.