From: dblack@...
Date: 2006-09-15T17:44:22+09:00
Subject: Re: How to collect over two arrays then look back to one?

Hi --

On Thu, 14 Sep 2006, Peter Booth wrote:

> I am reading Ruby for Rails and Ruby Cookbock and delighted by the
> Array#find_all and Enumerable#collect methods. I'm wondering what the
> idiomatic way to do the following is?
>
> Two parallel arrays A, B . For each element n of A for which f(An) is true,
> is g(B[n-3:n+3]) true? Where B[n-3:n+3] refers to seven elements of B whose
> position is centered over An' position.
>
> Can the block inside Enumerable#collect know it's position inside the
> Enumerable? Can one collect two parallel arrays?

To answer the first question: no.  You are free to join Citizens for
map_with_index, of which I am the founder and president :-)


David

-- 
                   David A. Black | dblack@wobblini.net
Author of "Ruby for Rails"   [1] | Ruby/Rails training & consultancy [3] 
DABlog (DAB's Weblog)        [2] | Co-director, Ruby Central, Inc.   [4]
[1] http://www.manning.com/black | [3] http://www.rubypowerandlight.com
[2] http://dablog.rubypal.com    | [4] http://www.rubycentral.org