From: Gavin Sinclair <gsinclair@...>
Date: 2004-09-21T10:22:14+09:00
Subject: Re: Array#index block and rdetect

On Tuesday, September 21, 2004, 1:30:12 AM, Yukihiro wrote:

> |Question: if "index" is a basic Enumerable thing, why is there no
> |Enumerable#each_index?  (My preference would be to push
> |#each_with_index down to the individual classes too; but in any case,
> |I'm curious about it.)

> "index" in "each_with_index" is a loop counter.  Perhaps wrong choice
> of the word.  It happen to be same index in Arrays.

I've never cared one way or the other about Hash#each_with_index.
It's pretty useless as the numbers tell you nothing meaningful.

When I want to iterate a hash completely, I use

  hash.each do |key, value| ... end

and that suits me fine.  But even that is rare because of the
meaningless output order.  So it's usually more like:

  hash.keys.sort.each do |key|
    value = hash[key]
    ...
  end

or

   hash.sort_by { |key, value| key }.each do |key, value|
     ...
   end

I don't see a real need for any methods to change.  Hash is clearly an
enumerable.  I see it as a collection of pairs/associations; that's
why I use Hash#each instead of the equivalent but redundant
Hash#each_pair.

Hash#each_with_index is useless, but I don't find it misleading.  The
very first time I ran 'ri Hash', I was able to work out what's going
on.  When you see Hash#each_pair and Hash#each_with_index, you know
that the "index" doesn't refer to keys.

If you defined Hash#each_with_index specially, instead of relying on
the Enumerable implementation, I guess this would be sensible:

  class Hash
    def each_with_index
      each_pair do |key, value|
        yield(value, key)
      end
    end
  end

Cheers,
Gavin