From: Austin Ziegler <austin@...>
Date: 2002-10-24T04:24:37+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (10/16/02)

On Thu, 24 Oct 2002 04:05:44 +0900, Mills Thomas (app1tam) wrote:
> It's not non-sensical. If it appeared that I mean for all objects
> to use append(), then I was not clear. Using append() was just an
> example. With numbers it might mean add_on(). With Strings it
> might mean Concat(). With Animals it might mean graft(). With
> TrainCars, it might mean hitch().
> 
> The point is, an object can have another object added to it. The
> fact that we do it easily with RealNumbers is only a cultural
> truism. It is not a stretch to think of graft() with an Animal.
> And so it is sensical. :-) (for non-english speakers, it is
> understandable).

It still remains non-sensical because it then becomes necessary to
create language exceptions for each type -- and each new type. With
Ruby's current behaviour, one only has to:

    def +(other)
    end

To get both + and += operators. As someone else pointed out, C++
defines + and += separately so that one or the other can be valid,
and they can do completely opposite things, at that. IMO, C++'s
model is the one that's nonsensical. (While the original C
implementation of += may not be = +, it acts like it.)

I think part of the problem in understanding why it's non-sensical
is that all variables in Ruby are references to objects. As others
pointed out:

    a = "foo"
    b = a
    b += "bar"
    p [a, b]

Under your model, then both variables would have the value "foobar".
Under Ruby's existing model, b no longer aliases a, but a new
string.

Ultimately, I think that any language that allows the definition of
+= separately from + is broken because it allows really dumb, really
broken things in exchange for a minor performance quibble. If you
explicitly want performance benefits in string concatenation, use
String#<< -- it's what I do. If I can't afford to take the chance of
modifying the original value, then I use +=.

-austin
-- Austin Ziegler, austin@halostatue.ca on 2002.10.23 at 15.14.29