From: Belorion <belorion@...>
Date: 2008-04-05T04:41:38+09:00
Subject: Re: The ||= assignment operator

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Thanks all, that clears up my understanding.  I hadn't thought of it as x =
x || "ruby" (even thoughI knew that x += 1 is the same as x = x + 1) and
that in that expanded case, x evaluates, logistically, to false if nil or
false.

Matt

On Fri, Apr 4, 2008 at 2:28 PM, Todd Benson <caduceass@gmail.com> wrote:

> On Fri, Apr 4, 2008 at 2:11 PM, Belorion <belorion@gmail.com> 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:
> >
> >  irb(main):001:0> x = true
> >  => true
> >  irb(main):002:0> x ||= "ruby"
> >  => true
> >  irb(main):003:0> x
> >  => true
> >  And, likewise, with nil:
> >
> >  irb(main):014:0> x = nil
> >  => nil
> >  irb(main):015:0> x ||= "ruby"
> >  => "ruby"
> >  irb(main):016:0> x
> >  => "ruby"
> >  However, I do not understand this behavior:
> >
> >  irb(main):019:0> x = false
> >  => false
> >  irb(main):020:0> x ||= "ruby"
> >  => "ruby"
> >  irb(main):021:0> x
> >  => "ruby"
> >
> >
> >  We know that false != nil, and yet the ||= will assign if the left hand
> side
> >  is false?
> >
> >  regards,
> >  Matt
>
> The operators are working with a three-valued logic.  In a comparison,
> a FalseClass object or a NilClass object will be logistically false.
>
> Todd
>
>

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