From: "David A. Black" <dblack@...>
Date: 2008-10-04T05:36:36+09:00
Subject: Re: Is Assignment in a Conditional an Idiom?

Hi --

On Sat, 4 Oct 2008, List.rb wrote:

> I just figured ruby was looking at the value of a returned from the 
> definition in the condition. The value of  'a' is still false after the 
> second condition.

Are you talking about this one?

   puts "Never reached" unless (a = nil) || (!a = a)

It's a peculiar line of code, but it's entirely logical. The
expression !a = a has to mean !(a = a), because !a isn't an lvalue.
Since a is nil, the expression a = a (or x = a, etc.) evaluates to
nil. So you've basically got:

   unless nil || nil

I might be misunderstanding the part you thought was questionable in
its logic.


David

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