Move containsObject: to NSOrderedSet.m. Make additional changes to fix issues pointed out by Fred

Source/GSOrderedSet.m

@@ -218,22 +218,6 @@ static Class	mutableSetClass;
   return item.obj;
 }
 
-- (BOOL) containsObject: (id)anObject
-{
-  NSUInteger i = 0;
-
-  for (i = 0; i < [self count]; i++)
-    {
-      id obj = [self objectAtIndex: i];
-      if([anObject isEqual: obj])
-	{
-	  return YES;
-	}
-    }
-  
-  return NO;
-}
-
 /* Designated initialiser */
 - (id) initWithObjects: (const id*)objs count: (NSUInteger)c
 {
@@ -308,6 +292,7 @@ static Class	mutableSetClass;
 
 - (void) removeObjectAtIndex: (NSUInteger)index
 {
+  _version++;
   GSIArrayRemoveItemAtIndex(&array, index);
 }
 

Source/NSOrderedSet.m

@@ -629,12 +629,16 @@ static SEL	rlSel;
   return 0;
 }
 
-- (BOOL)containsObject:(id)anObject // required override
+- (BOOL) containsObject: (id)anObject
 {
-  [self subclassResponsibility: _cmd];
-  return NO; 
+  NSUInteger i = [self indexOfObject: anObject];
+  if (i == NSNotFound)
+    {
+      return NO;
+    }
+  return YES;
 }
-
+    
 - (void) enumerateObjectsAtIndexes:(NSIndexSet *)indexSet
                            options:(NSEnumerationOptions)opts
                         usingBlock:(GSEnumeratorBlock)aBlock
@@ -727,7 +731,6 @@ static SEL	rlSel;
   return GS_IMMUTABLE(group);
 }
 
-    
 - (NSUInteger) indexOfObject:(id)anObject
 {
   NSUInteger	c = [self count];