From: Rick DeNatale <rick.denatale@...>
Date: 2010-06-08T04:18:39+09:00
Subject: Re: Question about abbreviated indexing assignments

On Mon, Jun 7, 2010 at 1:05 PM, Rein Henrichs <reinh@reinh.com> wrote:
> It is commonly thought that x <operator>= y is exactly equivalent to x = x
> <operator> y in all cases. What you have just demonstrated is that,
> presumably for performance reasons, h[key] ||= value is in fact equivalent
> to h[key] || h[key] = value, rather than h[key] = h[key] || value. This
> prevents a second lookup in the case where k[key] exists and is not nil or
> false.
>

x ||= y is NOT equivalent to x = x || y

Instead a closer approximation is

  x || x = y

http://talklikeaduck.denhaven2.com/2008/04/26/x-y-redux


-- 
Rick DeNatale

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