Index: src/OFMutableSet.h
==================================================================
--- src/OFMutableSet.h
+++ src/OFMutableSet.h
@@ -35,6 +35,21 @@
  * \brief Removes the specified object from the set.
  *
  * \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.
+ *
+ * \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
+ *	  set.
+ *
+ * \param set The set to intersect
+ */
+- (void)intersectSet: (OFSet*)set;
 @end

Index: src/OFMutableSet.m
==================================================================
--- src/OFMutableSet.m
+++ src/OFMutableSet.m
@@ -19,10 +19,11 @@
 #define OF_MUTABLE_SET_M
 
 #import "OFMutableSet.h"
 #import "OFDictionary.h"
 #import "OFNull.h"
+#import "OFArray.h"
 #import "OFAutoreleasePool.h"
 
 @implementation OFMutableSet
 - (void)addObject: (id)object
 {
@@ -37,10 +38,37 @@
 {
 	[dictionary removeObjectForKey: object];
 
 	mutations++;
 }
+
+- (void)minusSet: (OFSet*)set
+{
+	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
+	OFEnumerator *enumerator = [set objectEnumerator];
+	id object;
+
+	while ((object = [enumerator nextObject]) != nil)
+		[self removeObject: object];
+
+	[pool release];
+}
+
+- (void)intersectSet: (OFSet*)set
+{
+	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
+	OFArray *objects = [dictionary allKeys];
+	id *cArray = [objects cArray];
+	size_t count = [objects count];
+	size_t i;
+
+	for (i = 0; i < count; i++)
+		if (![set containsObject: cArray[i]])
+			[self removeObject: cArray[i]];
+
+	[pool release];
+}
 
 - (int)countByEnumeratingWithState: (of_fast_enumeration_state_t*)state
 			   objects: (id*)objects
 			     count: (int)count
 {

Index: tests/OFSet.m
==================================================================
--- tests/OFSet.m
+++ tests/OFSet.m
@@ -75,10 +75,22 @@
 	TEST(@"-[intersectsSet:]",
 	    [(set2 = [OFSet setWithObjects: @"x", nil]) intersectsSet: set1] &&
 	    [set1 intersectsSet: set2] &&
 	    ![([OFSet setWithObjects: @"1", nil]) intersectsSet: set1]);
 
+	TEST(@"-[minusSet:]",
+	    R([mutableSet minusSet: ([OFSet setWithObjects: @"x", nil])]) &&
+	    [mutableSet isEqual: ([OFSet setWithObjects: @"baz", @"bar", nil])])
+
+	TEST(@"-[intersectSet:]",
+	    R([mutableSet intersectSet: ([OFSet setWithObjects: @"baz",
+	    nil])]) && [mutableSet isEqual: ([OFSet setWithObjects: @"baz",
+	    nil])])
+
+	[mutableSet addObject: @"baz"];
+	[mutableSet addObject: @"x"];
+
 #ifdef OF_HAVE_FAST_ENUMERATION
 	ok = YES;
 	i = 0;
 
 	for (OFString *s in set1) {