Time for an 2014 update…

Task/Polymorphic-copy/Racket/polymorphic-copy-1.rkt

@@ -0,0 +1,18 @@
+#lang racket/base
+
+(define (copy-prefab-struct str)
+  (apply make-prefab-struct (vector->list (struct->vector str))))
+
+(struct point (x y) #:prefab)
+(struct point/color point (color) #:prefab)
+
+
+(let* ([original (point 0 0)]
+       [copied (copy-prefab-struct original)])
+  (displayln copied)
+  (displayln (eq? original copied)))
+
+(let* ([original (point/color 0 0 'black)]
+       [copied (copy-prefab-struct original)])
+  (displayln copied)
+  (displayln (eq? original copied)))

Task/Polymorphic-copy/Racket/polymorphic-copy-2.rkt

@@ -0,0 +1,16 @@
+;#lang racket
+
+(define point%
+  (class object%
+    (super-new)
+    (init-field x y)
+    (define/public (clone) (new this% [x x] [y y]))
+    (define/public (to-list) (list this% x y))))
+
+(define point/color%
+  (class point%
+    (super-new)
+    (inherit-field x y)
+    (init-field color)
+    (define/override (clone) (new this% [x x] [y y] [color color]))
+    (define/override (to-list) (list this% x y color))))