Implement ldict-contains? predicate.

doc/utils.md

@@ -49,11 +49,18 @@ populating it with initial data.
 If only one argument is given, the procedure checks whether it is a
 list of equality procedure and acts accordingly.
 
-    (ldict-empty? d)
+    (ldict-empty? ld)
 
-* ```d``` - a ldict instance
+* ```ld``` - a ldict instance
 
-Returns true if given dictionary contains no keys.
+Returns ```#t``` if given dictionary contains no keys.
+
+    (ldict-contains? ld k)
+
+* ```ld``` - a ldict instance
+* ```k``` - a key compatible with given ldict
+
+Returns ```#t``` if given ```ld``` contains given key ```k```.
 
 ### IO
 

src/util-dict.scm

@@ -34,8 +34,9 @@
 
   ldict-empty?
   
-  ldict-has-key?
+  ldict-contains?
   ldict-ref
+  
   ldict-remove
   ldict-set
   ldict-keys
@@ -76,15 +77,21 @@
  ;; Convenience accessors
  (define ldict-meta cadr)
  (define ldict-equality? caadr)
- (define ldict-list cddr)
+ (define ldict-pairs cddr)
 
  ;; Returns true if given dictionary contains no keys
- (define (ldict-empty? d)
-   (null? (ldict-list d)))
+ (define (ldict-empty? ld)
+   (null? (ldict-pairs ld)))
 
  ;; Checks whether given dictionary d contains the key k.
- (define (dict-has-key? d k)
-   (if (assq k d) #t #f))
+ (define (ldict-contains? ld k)
+   (let ((equality? (ldict-equality? ld)))
+     (let loop ((pairs (ldict-pairs ld)))
+       (if (null? pairs)
+	   #f
+	   (if (equality? (caar pairs) k)
+	       #t
+	       (loop (cdr pairs)))))))
 
  ;; Retrieves the value for key k from dictionary d. If third argument
  ;; is provided it is used as default value in case the key does not