From: James Gray <james@...>
Date: 2009-02-07T00:40:05+09:00
Subject: Re: iterating over two arrays simultaneously

On Feb 6, 2009, at 9:24 AM, Jean-Denis Muys wrote:

> James' solution to the previous question being so much better than  
> mine (which I did for my learning purposes),

I think your solution was just fine.

> I dare asking about how to iterate over two arrays in parallel. I  
> don't see a way to use the iteration methods, and my solution below  
> doesn't feel idiomatic at all:
>
> array1 = [1, 2, 3]
> array2 = ["one", "two", "three"]
> # note: both arrays are known to be the same size
>
> (0..array1.size-1).each {
>  | i |
>  print "#{array2[i]} = #{array1[i]}\n"
> }

Here's one way:

 >> array1 = (1..3).to_a
=> [1, 2, 3]
 >> array2 = %w[one two three]
=> ["one", "two", "three"]
 >> array1.zip(array2) { |num, word| puts "#{num} #{word}" }
1 one
2 two
3 three
=> nil

and another:

 >> require "generator"
=> true
 >> SyncEnumerator.new(array1, array2).each { |num, word| puts "#{num}  
#{word}" }
1 one
2 two
3 three
=> #<SyncEnumerator:0x1115e58 @gens=[#<Generator:0x1115de0  
@cont_endp=#<Continuation:0x11154bc>, cont_yieldnil, queue[],  
block#<Proc:0x0111e15c@/usr/local/lib/ruby/1.8/generator.rb:71>,  
cont_next#<Continuation:0x1115624, @index=3>, #<Generator:0x1115cc8  
@cont_endp=#<Continuation:0x111546c>, cont_yieldnil, queue[],  
block#<Proc:0x0111e15c@/usr/local/lib/ruby/1.8/generator.rb:71>,  
cont_next#<Continuation:0x1115570, @index=3>]

Hope that helps.

James Edward Gray II