From: Daniel Berger <djberge@...>
Date: 2003-04-25T08:20:08+09:00
Subject: Re: Hashes and Enumerable#each_with_index

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?

This operation seems most sensical, to me, when used with ordered
hashes.  Here's a patch for Gotoken's "pseudohash" package on the RAA:

# add to pseudohash.rb (not heavily tested)
def [](k)
  if k.kind_of?(Fixnum)
     key = order[k]
     return self.fetch(key)
  else
     return super
  end
end

def each_with_index
   rest = keys - order
   order.each{|k,v| yield(k,self[k],order.index(k)) if include?(k)}
   rest.each{|k,v| yield(k,self[k],order.index(k)) }
end

example:

record = PseudoHash.new.with_order ['Alice', 'Bob', 'Charlee']
record['Charlee'] = 90
record['Alice'] = 91
record['Bob'] = 89
record.each_with_index{|k,v,i|
   puts "Key: #{k}"
   puts "Index: #{i}"
   puts "Using index: " + record[i].to_s
   puts "Using key: " + record[k].to_s
   puts "=" * 10
}

Regards,

Dan

a = [74, 117, 115, 116, 32, 65, 110, 111, 116, 104, 101, 114, 32, 82]
a.push(117,98, 121, 32, 72, 97, 99, 107, 101, 114)
puts a.pack("C*")