Making immutable instances

Mike Meyer mwm at
Fri Dec 2 01:18:55 CET 2005

Paul Rubin <> writes:
> Mike Meyer <mwm at> writes:
>> Lots of people seem to want immutable instances. Nobody seems to have
>> a use case for them.
> What is the use case for immutable strings?  Why shouldn't strings be
> mutable like they are in Scheme?

I don't know. Why shouldn't they?

> Generally if I know I don't plan to mutate something, I'd want to make
> it immutable so the runtime system can notice if I make an error.
> It's like an "assert" statement spread through the whole program.

That's not a use case, that's a debugging aid. The same logic applies
to adding type declarations, private/public/etc. declerations, and
similar B&D language features. It's generally considered that it's not
a good enough reason for adding those, so it doesn't really constitute
a good enough reason for making an instance immutable.

Mike Meyer <mwm at>
Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information.

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