From: Zsban Ambrus <ambrus@...>
Date: 2004-04-18T04:47:39+09:00
Subject: Re: Hash, ==,  key-value comparison

On Fri, Apr 16, 2004 at 09:23:00AM +0900, nobu.nokada@softhome.net wrote:
> Hi,
> 
...
> 
> I feel Hash#=== would test membership, i.e., alias for
> Hash#key?.
> 
> -- 
> Nobu Nakada

I'd agree with that. This way you could easily test for many possible
values in a case statement. 

Note that if there are many vaes to match with, then a hash may be 
more efficent then a "when" with a comma-delimited list, as long as the
hash is calculated only once.  (Of course, if there are multiple "when"
branches like that, a single hash that does all the matching or probably a
hash of proces or lambdas (I don't quite know the fine point of
distinguishing these) is better.)

Let me mention how this will work in perl6. In perl6, the =~ operator will
do something similar to ruby's ===, that is, it is used in the when clauses,
it matches numeric or string data, regexps, and classes just like === in
ruby (and thus does not automatically coerce a string to a regexp as =~ in
per5 or ruby). When it meets a hash or an array on either side, it mathces
each key (element of array) with the other side until it finds a match.
To do this with an array is quite unneccesarry I think, but it is good for a
haash.