From: "David A. Black" <dblack@...>
Date: 2008-05-02T07:10:56+09:00
Subject: Re: Please explain nuances of ||=

Hi --

On Fri, 2 May 2008, Phillip Gawlowski wrote:

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> David A. Black wrote:
> | Hi --
> |
> | On Fri, 2 May 2008, Phillip Gawlowski wrote:
> |
> | Whoops -- sorry :-)
>
> As if. :P
>
> | I actually have a feeling we're talking at cross-purposes, and that
> | I'm somehow not getting something. All I'm saying is that h[x] ||=
> | value is the same as h[x] || h[x] = value, for any hash h and any key
> | x. That can be demonstrated easily (as Robert did) just by
> | substituting one expression for the other. It's an unusual case, but
> | it's legal. I'm not sure what would be needed beyond that to
> | demonstrate that x = x || y is not a drop-in replacement for x ||= y.
>
> Yeah, I'm taking the Bird's Eye View on it all, essentially saying: 'it
> works like this almost always, but Hash is a special case, since it has
> default values [or whatever the implementation detail is, that makes
> Hash work differently]).

It's possible to generalize it; someone in one of the threads wrote a
class that showed the same behavior, but I can't remember the details.
I do wish it were otherwise; it's definitely unexpected, I think.


David

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