From: Chris Shea <cmshea@...>
Date: 2008-04-05T05:15:08+09:00
Subject: Re: The ||= assignment operator

On Apr 4, 1:30 pm, Paul Mucur <mu...@waferbaby.com> wrote:
> On 4 Apr 2008, at 20:11, Belorion wrote:
>
> > It was my understanding that the ||= assignment operator assigned
> > the value
> > on the right-hand side if and only if the left hand side did not
> > already
> > have a value:
>
> It's probably better to think of x ||= "ruby" as being short hand for
> x = x || "ruby" (which it effectively is) instead of "assign if not
> already having a value". If you do this, then you can see why your
> last example behaves like it does.
>
> Don't forget that there are other similar operators like +=, -= and
> &&= and they all follow the same pattern:
>
> x ?= y
> x = x ? y
>
> Where ? is one of -, +, && or ||.
>
> Hope that this helps.

It's better to think of x ||= "ruby" as x || x = "ruby".

--
h = Hash.new('default value')

h[:test] ||= 'assigned value'
h # => {}

# same as:
h[:test] || h[:test] = 'assigned value'
h # => {}

# not:
h[:test] = h[:test] || 'assigned value'
h # => {:test=>"default value"}
--

Chris