From: Austin Ziegler <austin@...>
Date: 2002-10-25T02:06:45+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (10/16/02)

On Thu, 24 Oct 2002 20:21:54 +0900, dblack@candle.superlink.net 
wrote:
> On Thu, 24 Oct 2002, William Djaja Tjokroaminata wrote:
>> Therefore, a person with a C++ background, who is used to
>> avoiding the creation of unnecessary intermediate objects, will
>> be surprised that Ruby does it *all the time* in its '+='
>> operator. (Furthermore, the creation of equivalent intermediate
>> objects may even be more "expensive" in Ruby than in C++ in
>> absolute terms.)
> 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.

It's creating an intermediate object that then becomes the original
object, in a sense. I think that the C++ programmer -- where
references are often used like "safe" or "pretty" pointers, would
expect the following code to print out the same Object#ID both times
-- and it doesn't. It doesn't because you're creating a composite
object (a + "bar") and then making a refer to that object rather
than the original a.

    a = "Foo"
    puts "a.id: #{a.id}"
    a += "bar"
    puts "a.id: #{a.id}"

I can see where it might be confusing, but as long it's made clear
that a += b is the same as a = a + b, then even C++ programmers
shouldn't expect a to point to the same object any longer (because
'+' would likely create an intermediate object).

-austin
-- Austin Ziegler, austin@halostatue.ca on 2002.10.24 at 12.59.45