From: Stefano Crocco <stefano.crocco@...>
Date: 2010-12-26T17:59:38+09:00
Subject: Re: array index inside map function

On Sunday 26 December 2010 17:47:19 Peter Vandenabeele wrote:
> Siddharth Venkatesan wrote in post #970728:
> > Hi all,
> > 
> > how can i access the index of the element inside the map argument block?
> > 
> > "101010,234,876".split(",").map {|c| get_something(c)}
> > 
> > this works. But the problem is i need to apply the get_something on only
> > the
> > second and third element of the array. How can I check the index of the
> > element inside the map block?
> 
> There is each_with_index, but that has the "each" functionality
> and not the "map"/"collect" functionality.
> 
> That would be (not tested):
>   result = []
>   "101010,234,876".split(",").each_with_index {|c, i| result <<
> do_something(c,i)}
> 
> HTH,
> 
> Peter

If you're using ruby 1.8.7 or later, calling each_with_index without a block 
returns an enumerator, so that you can write something like:

"101010,234,876".split(",").each_with_index.map do |c, i| 
  i == 1 or i == 2 ? get_something(c) : c
end

I hope this helps

Stefano