From: Robert Klemme <shortcutter@...>
Date: 2006-06-22T06:03:33+09:00
Subject: Re: The difference between s=s+”a” ans s<< ”a”

2006/6/21, Simon Kr�ger <SimonKroeger@gmx.de>:
> I think
>   s = s + "a" #
> or
>   s += "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)

I use the rule exactly the other way round: usually use << unless that
might cause problems.  There's a lot of code out there that does +=
while all it wants to do is appending.  += is less efficient and with
my C++ background << more looks like "append".

> Have a look at this:
> --------------------------------------
> def greet_matz greeting
>   greeting << ' matz!'
>   puts greeting
> end
>
> def greet_nobu greeting
>   greeting << ' nobu!'
>   puts greeting
> end
>
> hello = 'hello'
> greet_matz hello
> greet_nobu hello
> --------------------------------------
> #=> hello matz!
> #=> hello matz! nobu!
>
> you will get what you expect if you use +=

It depends on what you expect.  If methods are expected to get
something that they append stuff to then the observed behavior is
exactly what you expect and want.  :-)

For example, if you write a method that should append info about the
current instance to something then you should use << because then even
an IO object can be passed and the code still works as expected.

As generally, you should know your tools and be knowing what you do. :-)

Kind regards

robert

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