chickadee » chicken » special-forms » define-record-printer

Defines a printing method for record of the type NAME by associating a procedure with the record type. When a record of this type is written using display, write or print, then the procedure is called with two arguments: the record to be printed and an output-port.

(define-record-type foo (make-foo x y z) foo?
  (x foo-x)
  (y foo-y)
  (z foo-z))
(define f (make-foo 1 2 3))
(define-record-printer (foo x out)
  (fprintf out "#,(foo ~S ~S ~S)"
           (foo-x x) (foo-y x) (foo-z x)) )
(define-reader-ctor 'foo make-foo)
(define s (with-output-to-string
              (lambda () (write f))))
s                                   ==> "#,(foo 1 2 3)"
(equal? f (with-input-from-string
              s read)))             ==> #t