From: "Mikael Høilund" <mikael@...>
Date: 2008-06-13T07:26:01+09:00
Subject: Re: ||=

On Jun 13, 2008, at 0:08, Mike Cargal wrote:
> this really is equivalent to a = a || b, just like a += 1 is  
> equivalent to a = a + 1 (same for -=, etc.

However, be aware that this particular operator has an optimization  
making it behave like

a || a = b

instead. Example problem:

 >> h = Hash.new() { "default" } # Makes a Hash with "default" as the  
default value instead of nil
=> {}
 >> h[:a]
=> "default"
 >> h.has_key? :a
=> false

 >> h[:a] ||= "not default"
=> "default"
 >> h[:a]
=> "default"
 >> h.has_key? :a
=> false

 >> h[:a] = h[:a] || "not default"
=> "default"
 >> h[:a]
=> "default"
 >> h.has_key? :a
=> true
 >>

-- 
# Mikael Høilund
def method_missing(m, a=0) a +
m.to_s[/[a-z]+/].size * 2; end
p What is the meaning of life?