This class extends the interface of NSCharacterSet to allow clients to modify the contents of the character set after it has been initialized. Clients may add and remove characters specified in a string or numeric range, and new sets may be created from the union or intersection of two existing sets.

@interface NSMutableCharacterSet : NSCharacterSet <NSCopying, NSMutableCopying>
// Instance Methods
- (void)addCharactersInRange:(NSRange)aRange;
- (void)addCharactersInString:(NSString *)aString;
- (void)formIntersectionWithCharacterSet:(NSCharacterSet *)otherSet;
- (void)formUnionWithCharacterSet:(NSCharacterSet *)otherSet;
- (void)invert;
- (void)removeCharactersInRange:(NSRange)aRange;
- (void)removeCharactersInString:(NSString *)aString;
// Methods Implementing NSCopying
- (id)copyWithZone:(NSZone *)zone;
// Methods Implementing NSMutableCopying
- (id)mutableCopyWithZone:(NSZone *)zone;