Index: src/OFMutableSet.h
==================================================================
--- src/OFMutableSet.h
+++ src/OFMutableSet.h
@@ -33,21 +33,21 @@
  * @param object The object to remove from the set
  */
 - (void)removeObject: (id)object;
 
 /*!
- * @brief Removes all objects from the receiver that are in the specified set.
+ * @brief Removes all objects from the receiver which are in the specified set.
  *
  * @param set The set whose objects will be removed from the receiver
  */
 - (void)minusSet: (OFSet*)set;
 
 /*!
- * @brief Removes all objects from the receiver that are not in the specified
+ * @brief Removes all objects from the receiver which are not in the specified
  *	  set.
  *
- * @param set The set to intersect
+ * @param set The set to intersect with
  */
 - (void)intersectSet: (OFSet*)set;
 
 /*!
  * @brief Creates a union of the receiver and the specified set.

Index: src/OFSet.h
==================================================================
--- src/OFSet.h
+++ src/OFSet.h
@@ -142,10 +142,34 @@
  * @return Whether the receiver and the specified set have at least one object
  *	   in common
  */
 - (BOOL)intersectsSet: (OFSet*)set;
 
+/*!
+ * @brief Creates a new set which contains the objects which are in the
+ *	  receiver, but not in the specified set.
+ *
+ * @param set The set whose objects will not be in the new set
+ */
+- (OFSet*)setBySubtractingSet: (OFSet*)set;
+
+/*!
+ * @brief Creates a new set by creating the intersection of the receiver and
+ *	  the specified set.
+ *
+ * @param set The set to intersect with
+ */
+- (OFSet*)setByIntersectingWithSet: (OFString*)set;
+
+/*!
+ * @brief Creates a new set by creating the union of the receiver and the
+ *	  specified set.
+ *
+ * @param set The set to create the union with
+ */
+- (OFSet*)setByAddingSet: (OFSet*)set;
+
 #ifdef OF_HAVE_BLOCKS
 /*!
  * @brief Executes a block for each object in the set.
  *
  * @param block The block to execute for each object in the set

Index: src/OFSet.m
==================================================================
--- src/OFSet.m
+++ src/OFSet.m
@@ -389,10 +389,46 @@
 
 	objc_autoreleasePoolPop(pool);
 
 	return [element autorelease];
 }
+
+- (OFSet*)setBySubtractingSet: (OFSet*)set
+{
+	OFMutableSet *new;
+
+	new = [[self mutableCopy] autorelease];
+	[new minusSet: set];
+
+	[new makeImmutable];
+
+	return new;
+}
+
+- (OFSet*)setByIntersectingWithSet: (OFSet*)set
+{
+	OFMutableSet *new;
+
+	new = [[self mutableCopy] autorelease];
+	[new intersectSet: set];
+
+	[new makeImmutable];
+
+	return new;
+}
+
+- (OFSet*)setByAddingSet: (OFSet*)set
+{
+	OFMutableSet *new;
+
+	new = [[self mutableCopy] autorelease];
+	[new unionSet: set];
+
+	[new makeImmutable];
+
+	return new;
+}
 
 #if defined(OF_HAVE_BLOCKS) && defined(OF_HAVE_FAST_ENUMERATION)
 - (void)enumerateObjectsUsingBlock: (of_set_enumeration_block_t)block
 {
 	BOOL stop = NO;