Implement and document new ldict-map.

src/util-dict.scm

@@ -41,10 +41,13 @@
   ldict-set
   
   ldict-keys
+  
   ldict-map
   ldict-filter
   ldict-reduce
+  
   ldict-update
+  
   ldict-tests!
   )
 
@@ -151,18 +154,20 @@
  ;; Maps dictionary values, the procedure gets key-value pairs if it
  ;; accepts more than one argument. If it accepts a third argument,
  ;; index gets passed as well.
- (define (dict-map proc d)
+ (define (ldict-map proc ld)
    (let* ((lpi (length (procedure-information proc)))
 	  (both? (> lpi 2))
 	  (index? (> lpi 3)))
-     (let loop ((d d)
-		(r '())
+     (let loop ((pairs (ldict-pairs))
+		(res '())
 		(i 0))
-       (if (null? d)
-	   r ; No reverse needed, order does not matter
-	   (loop (cdr d)
-		 (let ((k (caar d))
-		       (v (cdar d)))
+       (if (null? pairs)
+	   (cons TAG-LDICT
+		 (cons (ldict-meta ld)
+		       res))
+	   (loop (cdr pairs)
+		 (let ((k (caar pairs))
+		       (v (cdar pairs)))
 		   (cons (cons k (if both?
 				     (if index?
 					 (proc k v i)