Initial data commit

Task/Polymorphic-copy/TXR/polymorphic-copy.txr

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+(defstruct base ()
+  (:method identify (self) (put-line "base")))
+
+(defstruct derived (base)
+  (:method identify (self) (put-line "derived")))
+
+(defstruct poly ()
+  obj
+
+  (:method deep-copy (self)
+    (let ((c (copy self))) ;; make copy of s
+      (upd c.obj copy)     ;; copy self's obj
+      c)))                 ;; return c
+
+;; Test
+
+(let* ((b (new base))
+       (d (new derived))
+       (p (new poly obj d)))
+  b.(identify) ;; prints base
+  d.(identify) ;; prints derived
+
+  (let ((c p.(deep-copy)))
+    p.obj.(identify) ;; prints derived
+    (prinl (eq p.obj c.obj)))) ;; prints nil: c.obj is not a ref to p.obj