From: Robert Dober <robert.dober@...>
Date: 2006-06-22T06:10:16+09:00
Subject: Re: The difference between s=s+”a” ans s<< ”a”

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On 6/21/06, Simon Kr=F6ger <SimonKroeger@gmx.de> wrote:
>
> Robert Dober wrote:
> > On 6/21/06, Alan Moen <mapsetah2000-maillist5@yahoo.ca> wrote:
> >>
> >> Hi,
> >>
> >> I wonder what is the difference between s=3Ds+"a" ans s<< "a"?
> >
> >
> > s =3D s + "a"
> > (1) compute a new String object "s" + a
> > (2) set s as a reference to the newly created object
> >
> > s<<"a"
> >
> > (1) append "a" to the String object s refers to.
> >
> > The latter is much faster and should be prefered when possible (it will
> not
> > be possible if s is frozen e.g.)
>
> I think
>   s =3D s + "a" #
> or
>   s +=3D "a"
>
> should be the norm as long as you do not know that using it will cause
> you problems (really only performance problems come to my mind)


s << "a"
is just what you should do instead
of
s =3D s+ "a"
unless of course you get paid for GC ;)



Have a look at this:
> --------------------------------------
> def greet_matz greeting
>   greeting << ' matz!'
>   puts greeting
> end


Calling writer methods on parameters is asking for side effects, that might
be good or bad, I do not want to discuss that right now, but has *nothing*
to do with the question of the OP.

def greet_nobu greeting
>   greeting << ' nobu!'
>   puts greeting
> end
>
> hello =3D 'hello'
> greet_matz hello
> greet_nobu hello
> --------------------------------------
> #=3D> hello matz!
> #=3D> hello matz! nobu!
>
> you will get what you expect if you use +=3D


 Forgive me for being blunt: I will get what I expect if I use <<, I might
not get what you expected.

cheers
>
> Simon


Fortunately I did not state my favorite way to use puts
   puts some_variable * 1 << "some text" << ...
;)

Cheers
Robert




--=20
Deux choses sont infinies : l'univers et la b=EAtise humaine ; en ce qui
concerne l'univers, je n'en ai pas acquis la certitude absolue.

- Albert Einstein

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