From: Robert Klemme <shortcutter@...>
Date: 2009-12-23T17:28:00+09:00
Subject: Re: newbie: if is not null else...

2009/12/23 Stefano Crocco <stefano.crocco@alice.it>:
> On Wednesday 23 December 2009, Joshua Ballanco wrote:
>> |> $x ||= '-'
>> |>
>> |>
>> |>
>> |> This is a short form for
>> |>
>> |>
>> |>
>> |> $x = $x || '-'
>> |
>> |Correction, it is short form for:
>> |
>> |$x || $x = '-'
>> |
>> |...trust me, we've been over this at least 3 times, at great length, on
>> |the mailing list. ;-)
>
> I may be missing something, but according to page 96 of "The Ruby Programming
> Language", my version seems to be the correct one. It states that:
>
> results ||= []
>
> expands to
>
> results = results || []

For a simple assignment the difference is negligible but it matters if you do

h = {}
h[1] ||= 2

Please search the archives, Josh is right.  Btw, you can easily prove
it by doing

irb(main):001:0> x = Class.new { def a;puts "a";@a;end; def a=(x);puts
"a=";@a=x;end }.new
=> #<#<Class:0x10135234>:0x10134d10>
irb(main):002:0> x.a ||= 123
a
a=
=> 123
irb(main):003:0> x.a ||= 456
a
=> 123
irb(main):004:0> x.a = x.a || 789
a
a=
=> 123
irb(main):005:0>

If you were right the output of line 3 would look like the one of line 4.

Kind regards

robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/