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From: thomasw@hpcupt1.cup.hp.com (Thomas Wang)
Newsgroups: comp.object
Subject: value semantic versus reference semantic
Message-ID: <68780001@hpcupt1.cup.hp.com>
Date: 6 May 91 17:45:59 GMT
Organization: Hewlett Packard, Cupertino
Lines: 24


I am looking at the issues of value semantic versus reference semantic.

The value semantic says that  a := b;  means the value of 'b' is copied
to 'a'.

The reference semantic says that  a := b;  means 'a' is pointing to the
same place as 'b'.

It has occurred to me that value semantic is equivalent to reference
semantic if the value of 'b' can never change.  So one can use reference
semantic on immutable classes, and expect them to be well behaved.

However, it seems the running speed of program using immutable classes
can be slower than an equivalent program using mutable classes, since so many
garbage objects can be generated by the immutable version.
The question is 'are there optimization algorithms that can improve
the performance of immutable classes?'
 

 -Thomas Wang
              (Everything is an object.)
                                                     wang@hpdmsjlm.cup.hp.com
                                                     thomasw@hpcupt1.cup.hp.com