rework of gmi:match-link procedure

gmi.rkt

@@ -156,16 +156,6 @@
    (document-items document)))
 
 (define (match-link document id)
-  (define (iter next-structure)
-    (cond
-      [(and (link? (car next-structure))
-            (= (link-id (car next-structure)) id))
-       (link-url (car next-structure))]
-
-      [(empty? (cdr next-structure))
-       #f]
-
-      [else
-       (iter (cdr next-structure))]))
-
-  (iter (document-items document)))
+  (let ([link (findf (λ (link) (= (link-id link) id))
+                     (filter link? (document-items document)))])
+    (if link (link-url link) #f)))