From: Rick DeNatale <rick.denatale@...>
Date: 2009-08-27T09:46:18+09:00
Subject: Re: ||= with 1.8 and 1.9 ?

On Wed, Aug 26, 2009 at 7:00 PM, Yukihiro Matsumoto<matz@ruby-lang.org> wrote:
> Hi,
>
> In message "Re: ||= with 1.8 and 1.9 ?"
>    on Thu, 27 Aug 2009 01:20:20 +0900, Rick DeNatale <rick.denatale@gmail.com> writes:
>
> |a = b = c
> |
> | is treated the same as
> |
> |b = c; a = c
> |
> |in other words the result of the b= is ignored.
>
> No,
>
>  a = b = c
>
> is parsed as
>
>  a = (b = c)

Yes, I was speaking a bit loosely and was trying to say just what you said next

> so, result of the latter assignment is used for the former assignment.
> The point is when b here is an attribute assignment (e.g. foo.b = c),
> the result value from the setter method (b=) is ignored.

And I think that the really important point here is that

a.b ||= c

should have have the same effect as

a.b || a.b = c

And that it's surprising that in Ruby 1.9 it doesn't

puts RUBY_VERSION

class OrOrEquals
  def test
    @test
  end

  def test=(test)
    @test = test
    'not test'
  end
end

o = OrOrEquals.new

direct = o.test = 'a test'
p direct
o.test = nil
with_oror = o.test ||= 'a test'
p with_oror

with_or_or_assign = o.test || o.test = "a test"
p with_or_or_assign

$ multiruby or_or_equals.rb
/opt/local/lib/ruby/site_ruby/1.8/rubygems/source_index.rb:144:
warning: /Users/rick/.gem/ruby/1.8/specifications: Permission denied

VERSION = 1.8.6-p368
CMD     = ~/.multiruby/install/1.8.6-p368/bin/ruby or_or_equals.rb

1.8.6
"a test"
"a test"
"a test"

RESULT = 0

VERSION = 1.8.7-p160
CMD     = ~/.multiruby/install/1.8.7-p160/bin/ruby or_or_equals.rb

1.8.7
"a test"
"a test"
"a test"

RESULT = 0

VERSION = 1.9.1-p0
CMD     = ~/.multiruby/install/1.9.1-p0/bin/ruby or_or_equals.rb

1.9.1
"a test"
"not test"
"a test"

RESULT = 0


-- 
Rick DeNatale

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