From: Simon Krahnke <overlord@...>
Date: 2008-05-02T21:35:06+09:00
Subject: Re: Please explain nuances of ||=

* Rick DeNatale <rick.denatale@gmail.com> (03:26) schrieb:

> 1) In Ruby x ||= y does no assignment if x evaluates to true, and x
> &&= y does no assignment if x evaluates to true.

Eh, what? You are confusing me.

&&= does an assignment only if x evaluates to true.

The question of if there is an assignment in x = x is purely
metaphysical: there is no way to tell.

> 2) x || x = y, and x && x = y are much better first approximations of
> how x ||= y and x &&= y than x = x || y, and x = x && y, despite what
> K&R say.

And doesn't explain why x springs into existence, if didn't exist
before.

> 3) I say first approximations because of David Black's observation
> that x ||= y and x || x = y differ when x is undefined.

Right, but x = x || y doesn't.

The only thing special about x ||= y is that x is only ever evaluated
once. But that's special in every op=.

mfg,                   simon .... l