Implement and document predicates for ldict and lset.

doc/utils.md

@@ -49,6 +49,12 @@ 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? v)
+
+* ```v``` - any value
+
+Returns ```#t``` if given value is a ldict.
+
     (ldict-empty? ld)
 
 * ```ld``` - a ldict instance
@@ -213,6 +219,12 @@ This module implements linear-time set with custom comparator.
 
 Creates new lset with given comparator.
 
+    (lset? v)
+
+* ```v``` - any value
+
+Returns ```#t``` if given value is a lset.
+
     (lset-empty? ls)
 
 * ```ls``` - lset instance

src/util-dict-list.scm

@@ -32,6 +32,8 @@
   
   make-ldict
 
+  ldict?
+
   ldict-empty?
   
   ldict-contains?
@@ -76,6 +78,11 @@
 	   (loop (ldict-set ld (caar pairs) (cdar pairs))
 		 (cdr pairs))))))
 
+ ;; Returns true if given value is a ldict
+ (define (ldict? v)
+   (and (pair? v)
+	(eq? (car v) TAG-LDICT)))
+
  ;; Convenience accessors
  (define ldict-meta cadr)
  (define ldict-equality? caadr)

src/util-set-list.scm

@@ -32,6 +32,8 @@
 
   make-lset
 
+  lset?
+
   lset-empty?
 
   lset-member?
@@ -67,6 +69,11 @@
      (list TAG-LSET
 	   (list equality?))))
 
+ ;; Returns true if given value is lset
+ (define (lset? v)
+   (and (pair? v)
+	(eq? (car v) TAG-LSET)))
+
  ;; Convenience accessors
  (define lset-meta cadr)
  (define lset-equality? caadr)