From: Pete <pertl@...>
Date: 2006-06-22T06:44:50+09:00
Subject: Re: The difference between s=s+”a” ans s<< ”a”

Most readable + safe for me is e.g.:

puts "Hello, #{name}!"

puts "your calculation: #{arg1} * #{arg2} = #{arg1 * arg2}"

Robert Dober schrieb:
> On 6/21/06, Simon Kr�ger <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=s+"a" ans s<< "a"?
>> >
>> >
>> > s = 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 = 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)
>
>
> s << "a"
> is just what you should do instead
> of
> s = 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 = 'hello'
>> greet_matz hello
>> greet_nobu hello
>> --------------------------------------
>> #=> hello matz!
>> #=> hello matz! nobu!
>>
>> you will get what you expect if you use +=
>
>
> 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
>
>
>
>