From: Eleanor McHugh <eleanor@...>
Date: 2009-05-06T22:43:51+09:00
Subject: Re: '=||'

On 6 May 2009, at 13:03, Rick DeNatale wrote:
> The short circuiting only happens if the lhs expression returns a
> non-truthy value.
>
> Now it's true (I think) that "a op= b" is the same as "a = a op b" in
> C, Ruby ain't C.

:)

> Sometimes the stuff "under the hood" is a little more complicated than
> it first appears. <G>


Very true, and we all learn new stuff by considering it. For example I  
suspect quite a few people would be surprised by the following code:

class Test
   def initialize
     @switch = false
   end

   def [] x
     puts "[#{x}]"
     @switch = !@switch
   end

   def []= x, y
     puts "[#{x}] = #{y}"
   end
end

t = Test.new
t[:a] ||= 17
t[:a] ||= 17
t[:a] ||= 17

output:			[a]
				[a]
				[a]

here the '[]' call returns 'true' and 'false' by turns but in either  
event the assignment fails to call '[]='...


Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net
----
raise ArgumentError unless @reality.responds_to? :reason