From: matz@... (Yukihiro Matsumoto)
Date: 2002-11-28T13:57:55+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (11/24/02)

Hi,

In message "Re: Things That Newcomers to Ruby Should Know (11/24/02)"
    on 02/11/28, William Djaja Tjokroaminata <billtj@y.glue.umd.edu> writes:

|1) Why Fixnum is immutable (no Fixnum#succ!) while String is mutable
|(String#.succ! is provided)?

Numbers are immutable.  Partially because of performance.  Partially
because of Ruby's object model.  In Ruby, objects are values, not
place holders, so that numbers themselves are naturally immutable.

|2) How do I know which objects/classes are mutable and
|immutable?  (Answer: just read all the methods, and if no "!" methods are
|provided, it is immutable (?))

You don't have to care in general.  If you can't change the state of
the object, it is immutable.

							matz.