From: Jason Nordwick <jason@...>
Date: 2006-09-14T02:12:30+09:00
Subject: Re: How to collect over two arrays then look back to one?

I think...

a.values_at(*(0...a.size).to_a.select {|i| f(a[i]) && g([i-3,0].max..[i+3,a.size-1].min)})

Ruby seems a little verbose on this one.

-j



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?
> 
> Peter
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