From: benny <linux@...>
Date: 2004-01-28T20:34:54+09:00
Subject: Re: newbee question about "missing" hash methods +, += and <<

> >
> [dolio 04:59:10 ~]$ cat prac.rb
> #!/usr/bin/ruby
> 
> a = { 1 => 2 }
> b = { a => 3 }
> 
> p b
> 
> b.delete a
> 
> p b
> 
> [dolio 04:59:14 ~]$ ./prac.rb
> {{1=>2}=>3}
> {}
> 
> In your test, the { "foo" => "bar" } stored in the first hash wasn't the 
> same as the
> one you tried to delete later (different objects/ids, same structure). 
> Hashes for
> objects only have to be the same if #eql? returns true between them, and 
> that's
> not necessarily the case for two structrurally identical hashes (it's 
> true only if they're
> the same object).
> 
> As I recall, in Python you can only use immutable things as keys to hashes.
> However, in Java, for example, you can use any Object, whether it's a 
> String or
> a Hashtable, so Ruby isn't alone.
> 
> - Dan
> 

ok, thank you for your explanation: I learn a lot from that!

but when do we need such a thing? isn't it the contrast of the sense of an key and performance
hungry? 

benny