diff --git a/lib/vector.h b/lib/vector.h
index 7e00c39..deaf6a8 100644
--- a/lib/vector.h
+++ b/lib/vector.h
@@ -26,7 +26,7 @@
 /* struct for vector */
 struct _vector 
 {
-  unsigned int max;		/* max number of used slot */
+  unsigned int active;		/* number of active slots */
   unsigned int alloced;		/* number of allocated slot */
   void **index;			/* index to data */
 };
@@ -36,8 +36,13 @@
 
 /* (Sometimes) usefull macros.  This macro convert index expression to
  array expression. */
+/* Reference slot at given index, caller must ensure slot is active */
 #define vector_slot(V,I)  ((V)->index[(I)])
-#define vector_max(V) ((V)->max)
+/* Number of active slots. 
+ * Note that this differs from vector_count() as it the count returned
+ * will include any empty slots
+ */
+#define vector_active(V) ((V)->active)
 
 /* Prototypes. */
 vector vector_init (unsigned int size);