Immutable rules also take precedence over mutable ones. Immutable objects are therefore considered more "thread-safe" than mutable objects. A few languages, such as Objective-C, provide different types for mutable and immutable strings. Under Suber's initial ruleset, rules are divided into two types&colon; mutable and immutable. It may be possible to modify the values of (mutable) literals in program code. The stack pointer is a mutable register shared between all invocations. Objects of type codice 65 can refer to strings, but also to mutable buffers. This means that mutable objects and pointers can be shared between goroutines; see , below. The observer pattern is an alternative technique for handling changes to mutable objects. String functions are used to create strings or change the contents of a mutable string. Gemini, Virgo, Saggatarius and Pisces are mutable signs. For a mutable codice 33 object, its codice 34 can be written to. Pisces are the mutable water sign of the zodiac. Impure functional languages usually include a more direct method of managing mutable state. Both Java and the .NET Framework have mutable versions of string.