From: Yasushi Shoji <yashi@...>
Date: 2001-01-07T07:31:47+09:00
Subject: [ruby-talk:8766] Re: bug??

At Sat, 6 Jan 2001 13:00:46 +0900,
Mathieu Bouchard wrote:
> 
> > for the compatibility, the default Hash#key_missing should be
> > class Hash
> >   def key_missing(key)
> >     nil
> >   end
> > end
> > And my question is what functionality am I missing compare to
> > Hash@default and its accessors? (other than compatibility)
> 
> well, if instead it's
> 
> class Hash
>   def key_missing(key)
>     default
>   end
> end
> 
> then I don't think you're missing any functionality. Except that #[] (and
> such) call the internal Hash#default directly, so trying to
> overload/redefine it does not work. 

Hash#default and its accessors were added to prevent error with code
like:

hash = {}
...
hash["foo"] += 1

after the change so that nil + 1 yields error. [ruby-list:26602]

so having two ways (default and key_missing) to fix the same thing
isn't good IMHO.

Anyway, if we didn't have Hash@default yet, I'd vote for #key_missing
for sure, but don't know it worth breaking backward compatibity now.

I'll leave that decision for Matz.
--
         yashi