From: dblack@...
Date: 2003-04-25T07:40:47+09:00
Subject: Re: Hashes and Enumerable#each_with_index

Hi --

On Fri, 25 Apr 2003, Ryan Pavlik wrote:

> OK, looking at the archives I know this was discussed a few years ago,
> but there seems to be no real conclusion or improvement since then.
>
> The problem:  Hash#each_with_index returns an index that is not usable
> to address the hash.  That is, given the following:
>
>     h = Hash.new
>     h.each_with_index {
>         | o, i |
>         ...
>     }
>
> i is not defined such that h[i] == o, which is both misleading and
> seemingly useless.  (This behavior, as per the previous discussion, can
> be achieved with h.to_a.each_with_index.)
>
> Would it not be more useful to adopt the definiton of
> Enumerable#each_with_index where the index given is such that e[i] == o
> for any given Enumerable?

One problem I see is: how could you implement this, in Enumerable, in
terms of #each?

The current #each_with_index is essentially:

  i = 0
  each {|e| yield(e,i); i += 1}

If the new method (which I think should have a new name :-) did the
above for arrays, but did this for hashes:

  each {|k,v| yield(v,k)}

you'd be thrown back on defining something differently for different
classes that mixed in Enumerable.


David

-- 
David Alan Black
home: dblack@superlink.net
work: blackdav@shu.edu
Web:  http://pirate.shu.edu/~blackdav