From: Gordon Miller <gmiller@...>
Date: 2002-11-27T00:28:29+09:00
Subject: Re: each_with_index & collect_with_index?

> As for the second....  I recently appointed myself President of
> Citizens for MWI [map_with_indices], Inc.  (See
> <http://www.ruby-talk.org/51619>).  You may join the organization,
> free of charge :-)  Anyway, there's been a lot of talk of this at
> various points; if you search for map_with_index and map_with_indices
> on the ruby-talk archive, you'll see most of it.  Matz has recently
> indicated that he doesn't think there's a demand or need for it.  I'm
> still trying to keep the dream alive :-)
> 
> 

Doing numerically oriented algorithms I find myself frequently doing 
something like the following:

z = (1..5).to_a
a = (0..5).to_a
b = (0..5).to_a
c = z.collect_with_index { |el, i| f(el, a[i], b[i]) }

where f is some arbitrary function.

For the most part I have to create c as an empty array and push elements 
on to the array as I'm doing z.each_index.  The use of some sort of list 
comprehension-ish type of thing would be suitable as well, maybe 
something along the lines of a zip.

z =
a =   as before
b =
c = zip (z, a, b).collect { |el| f(el[0], el[1], el[2]) }

Though I think this was the discussion in another thread.

-- 
Gordon James Miller                 Bit Twiddlers, Inc
Software Architecture Architect     gmiller@bittwiddlers.com
                                     (571)330-9012