From: Gavin Sinclair <gsinclair@...>
Date: 2002-10-23T21:35:34+09:00
Subject: Re: Things That Newcomers to Ruby Should Know (10/16/02)

From: "Mauricio Fern�ndez" <batsman.geo@yahoo.com>

> On Wed, Oct 23, 2002 at 06:28:29PM +0900, Bulat Ziganshin wrote:
> > Hello Ian,
> >
> > Tuesday, October 22, 2002, 7:30:19 AM, you wrote:
> >
> > IM> I understand that, but since 'a' already exists prior to assigning a +
b
> > IM> to it, why does it need to be recreated? Where strings are concerned,
> > IM> I don't see why this would be any different to 'a << b'.
> >
> > main problem is that object pointed by 'a' mauy be also pointed by
> > another variable an if you change this object directly your code wil
> > have SIDE EFFECT. are you really need this? :) so '<<' and other
> > methods changing object itself must be used very carefully, preferably
> > for local variables and other "own" objects
> >
> > example of this side effect:
> >
> > def a(s)
> >   s << '!'
> >   s += '?'
> >   return s
> > end
> >
> > x='1'
> > y=a(x)
> > p x,y
>
> Would it be possible for Ruby to know whether an object is referenced by
> several variables so += does '<<' or '... = ... + ...' when appropriate?
>
> Perhaps a bit in each String indicating whether it is shared or
> not would make it... and GC issues could be ignored at first.

I don't think so.  += is syntax sugar for you-know-what.  Imagine trying to
explain to a newbie "... but except in this case ..."

Side-effects are a part of life in Ruby (and not only in Ruby).  Programmers
have to deal with them.  They're not even a bad thing.

Gavin