From: Robert Klemme <shortcutter@...>
Date: 2007-09-07T22:24:21+09:00
Subject: Re: assigning to hash keys when there is a default value?

2007/9/7, dblack@wobblini.net <dblack@wobblini.net>:
> > I believe it's not the only case.  Although x= and []= are different, it
> > seems in *both* cases assignment is not even invoked for ||=:
>
> True, but by "only *such* case" I meant: only case where evaluating
> the lhs and getting true doesn't tell the whole story, in terms of the
> functionality of the object, because of the defaulting to a value in
> the absence of a key.

Ah, ok.  Should've read more carefully.  I am sorry.

> I suppose one could argue that it isn't ||='s problem if the lhs is
> actually a kind of proxy. Nothing has yet convinced me, though, that
> ||= should not behave like x = x || y, even if the actual assignment
> gets optimized away.

Umm, now I am confused.  I thought the "optimized away" bit is the
critical bit - if you allow for this difference then they do actually
behave the same, don't they?

Btw, here's a possible explanation why the behavior is the way it is:
[]= and x= are usually costly operations (i.e. not just assignments
but methods doing some work) so avoiding that would help overall
performance.  Still I believe that's probably better than the
consistency although I usually tend to favor consistency as well.

Kind regards

robert