touch

pitfall/restructure/pointer.rkt

@@ -1,22 +1,21 @@
-#lang br
+#lang restructure/racket
 
 (define pointer-ks (make-hash))
 (define results (make-hash))
 
 (define vals '(a b (h) d e f g h i j))
 
-(for ([(val i) (in-indexed vals)])
-  (hash-ref! results i (λ ()
-                         (report* results i)
-                         (let/cc pointer-k
-                           (let ([v (cond
-                                      [(pair? val) (hash-set! pointer-ks (car val) pointer-k) (car val)]
-                                      [else val])])
-                             (define pointer (hash-ref pointer-ks v #f))
-                             (cond
-                               [pointer (hash-remove! pointer-ks v)
-                                        (pointer (format "~a xref" v))]
-                               [else v]))))))
-
-(for/list ([i (in-range (length (hash-keys results)))])
-  (hash-ref results i))
+(for ([(val i) (in-indexed vals)]
+      #:unless (hash-has-key? results val))
+  (hash-set! results i (let/cc pointer-k
+                         (cond
+                           [(hash-ref pointer-ks val #f) => (λ (pk)
+                                                              (hash-remove! pointer-ks val)
+                                                              (pk (format "~a@~a" val i)))]
+                           [(pair? val) (hash-set! pointer-ks (car val) pointer-k) 'tbd]
+                           [else val]))))
+(test-module
+ (check-equal?
+  (for/list ([i (in-range (length (hash-keys results)))])
+    (hash-ref results i))
+  '(a b "h@7" d e f g h i j)))