define-is-type-syntax-example-pt-a.sls

(import (define-is-type-syntax))

;; Define the pt type:

(define-record-type pt
  (fields (mutable x)
	  (mutable y)))

;; Generate the 'is-pt' macro:

(define-is-type-syntax is-pt
  pt
  (fields x y)
  (methods (neg pt-neg)))

;; Define a "method":

(define (pt-neg p)
  (make-pt (- (pt-x p))
	   (- (pt-y p))))

;; Define a pt:

(define p0 (make-pt 3 4))

;; Declare it to be a pt:

(is-pt p0)

;; Access the x field:

p0.x

;; Set the x field:

(p0.x! 7)

;; Call the 'neg' method:

(p0.neg)