From: "Hal E. Fulton" <hal9000@...>
Date: 2002-08-04T09:45:20+09:00
Subject: Re: Assoc Class (Hash Pairs)

----- Original Message ----- 
From: "Tom Sawyer" <transami@transami.net>
To: "ruby-talk ML" <ruby-talk@ruby-lang.org>
Sent: Saturday, August 03, 2002 7:15 PM
Subject: Re: Assoc Class (Hash Pairs)


> On Sat, 2002-08-03 at 16:40, Hal E. Fulton wrote:
> > Well, it's ordered, all right; but is it really a hash
> > any more? E.g., could you still get this to work?
> > 
> >   z = ordhash['a']     # equals 1
> > 
> > Not without changing the [] method of Array. And if you
> > change it in such a way, you're making Array into Hash.
> 
> no, not exactly. it's still array. you'd have to say: 
> 
>   z = ordhash[0]['a']
> 
> or
> 
>   z = ordhash[0].value

Yes, but that's my point: It's not a hash any more. It's
like an array of single-element hashes.

To find the value associated with key 'a', I'd have to 
*know* that 'a' was in ordhash[0].

Someone yesterday (?) posted an interesting use of 
Array#assoc... I think this is probably the "right" way to 
implement an ordered hash... and I wish I had thought of
that two years ago.
 
>   a = 'A'=>'The Letter A'
>   b = 'B'=>'The Letter B'
>   c = 'C'=>'The Letter C'
> 
>   puts a.index              # --> A
>   puts b.value              # --> The Letter B
> 
>   puts a['A']               # --> The Letter A
>   puts c['The Letter C']    # --> C

Hmm. Maybe.

>   a = 'A'
>   b = 'The Letter A'
> 
>   a => b
> 
>   puts a.assoc  # -->  The Letter A
> 
> thus having a way to association objects to one another, sort of like
> having varaible variable names.

Incompatible with the earlier suggestion, of course, since
a => b would be a valid Assoc value.
 
> just thinking out loud at this point.

Frequently a helpful thing!

Hal