From: Devin Mullins <twifkak@...>
Date: 2006-12-24T04:02:20+09:00
Subject: Re: Help with a ruby idiom

dblack@wobblini.net wrote:
> It is indeed functionally equivalent to those, though all of them
> would blow up :-)
Not all of them.
   a = b unless a
works, for the same reason you described
   a = a || b
working. Here, the "a =" is parsed before the "unless a" is evaluated.

But yes, a ||= b maps more closely to a = a || b, just like a += b maps 
to a = a + b.

Devin
(Though, I tend to use the ||= idiom most often with instance/class 
variables, who don't raise NameError like locals do.)