From: William Morgan <wmorgan-ruby-talk@...>
Date: 2005-07-11T02:37:57+09:00
Subject: Re: accessing index inside map (*_with_index)

Excerpts from daz's mail of  8 Jul 2005 (EDT):
> One major factor that has bugged me is the lack of symmetry
> between #each and #e_w_i which discourages temporary changes.
> 
>  h = {:a => 1, :b => 2, :c => 3}
> # Current conversion of Hash#each to #each_with_index
> 
>  h.each            {|ek, ev|  p [ek  , ev       ]}
>  h.each_with_index {|e, idx|  p [e[0], e[1], idx]}
> #      ^_________^      ^_^       ^_^  ^^_^  ^_^
> #           A            B         C   D C    E
>
> # A.  Change the method name to a much longer one.
> # B.  Name the index variable.
> # C.  Hash#each gives key and value -- #each_with_index
> #     passes these as a two-element array into the first
> #     block parameter.  Specify which element.
> # D.  The name you chose for the second block parameter of each
> #     will, probably, need changing (if you used, say, 'key, val').
> # E.  Use the index variable.

Minor point, but you can also do

   h.each_with_index { |(ek, ev), idx| p [ek, ev, idx] }

which solves C and D (though I guess introduces an "F").

-- 
William <wmorgan-ruby-talk@masanjin.net>