From: Russell Norris <rsl@...>
Date: 2007-09-03T22:32:21+09:00
Subject: Re: assigning to hash keys when there is a default value?

I learned that x ||= y means set x to y unless x, so I don't see the
bug. and i don't see this as being at all unpredictable. either way
you expect it to work, it either fails 100% or succeeds 100%. :) the
only problem is when you expect it to do something it doesn't do,
which is tautologically what every problem is i guess.

RSL

On 9/3/07, dblack@wobblini.net <dblack@wobblini.net> wrote:
> Hi --
>
> On Mon, 3 Sep 2007, Russell Norris wrote:
>
> > I don't think this is a bug, kittens. since h[2] returns a value [even
> > though it's not set], it causes h[2] to evaluate so the assignment
> > never happens. x ||= y just means give me x or set x to y if there's
> > no value for x. h[2] _does_ have a value if only a default one.
> >
> > just my two cents.
> >
> > unless i missed the point here, in which case i apologize for my hasty
> > conclusion. :))
>
> The thing is, this:
>
>    x ||= y
>
> always means (at least, so I've always been told):
>
>    x = x || y
>
> which in the case of the hash with a default value of 5, would mean:
>
>    h[2] = 5 || 10
>
> In other words: h.[]=(2, 5||10)
>
> At that point, the default value is out of the picture. The default
> value has no implications for the #[]= (writer) method; it's only what
> you get when you use the #[] (reader) method.
>
> So what's at stake here is the matter of x ||= y behaving predictably.
> I have to say, it's a case where I'm not even really concerned with
> the implementation (e.g., whether it uses [] on its way to []=) but
> just the semantics. I don't like the idea that the syntactic sugar is
> actually not a reliable drop-in replacement for the thing it's
> sugaring.
>
>
> David
>
> --
> * Books:
>    RAILS ROUTING (new! http://www.awprofessional.com/title/0321509242)
>    RUBY FOR RAILS (http://www.manning.com/black)
> * Ruby/Rails training
>      & consulting:  Ruby Power and Light, LLC (http://www.rubypal.com)
>
>