From: Brian Candler <B.Candler@...>
Date: 2003-07-21T23:59:50+09:00
Subject: Re: Proposal: Array#to_h, to simplify hash generation

On Mon, Jul 21, 2003 at 11:34:39PM +0900, Gavin Sinclair wrote:
> > I'm not sure how this differs from (rejected) RCR#12 (except for
> > having to return a key as well as a value).
> 
> How did O.J. Simpson's second trial differ from his first? ;)
> 
> Anyway, I think returning a key as well as a value is a significant
> difference:
>  - much more flexible (I create all kinds of hashes all the time in
>    my code, and could really use that flexibility)
>  - less magical, more scrutible: having two values makes it clear what
>    is going on, given that we're dealing with a hash.  With the
>    single-value to_hash/hashify, I had to keep reminding myself what
>    it meant; not so with the new "make_hash".

Can I suggest another name - "collect_hash" - since that's basically what it
is?

   collect {... return [x,y] }         =>>   [[a,b], [c,d], ...]
   collect_hash {... return [x,y] }    =>>   {a=>b, c=>d, ...}

In which case it clearly belongs in Enumerable - see Gavin's implementation
in [RubyTalk:76446]

It's still not an inverse operation to Hash#to_a, and I think there could
still be value in that. You could simulate it of course, using

   myhash = myarray.collect_hash { |pair| pair }

If we didn't have Hash#to_a then it could also be implemented as

   myarray = myhash.collect { |pair| pair }

But we do, so we don't bother.

Regards,

Brian.