From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-10-24T22:42:59+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (10/16/02)

dblack@candle.superlink.net wrote:

> I don't think "a += 'str'" (or whatever) is creating an intermediate
> object though, at least not in the sense that I understand the term.
> It's just performing an assignment, not doing anything extra.

Hi David,

Probably "intermediate" is not an exact terminology; maybe "new" object is
a better one?  This can be shown by

    a = 'str'
    puts a.id    # -> some number
    a << 'str'
    puts a.id    # -> number unchanged (in-place modification)
    a += 'str'
    puts a.id    # -> number changed (a new object is created)

I think people with C++ background are used to the concept or convention 
that '+=' means in-place modification while '= self + something' means a
new object creation.  I think that is how we usually control performance
in C++: we prefer to use '+=' unless the use of '=' is necessary.  The
aliasing/side-effects to other variables is of no concern because usually
the '=' operator is overloaded (but then if someone forgets to overload
the '=' operator then it may create a bug... :) )

Regards,

Bill