From: Brian Candler <b.candler@...>
Date: 2011-02-05T18:17:26+09:00
Subject: Re: Determining uniqueness on a single array element

James Byrne wrote in post #979694:
> Now I wish to ensure that each distinct hexdigest is processed but once.
> I can do this:
>
>    hex_array = []
>    outer_array.each do |inner_array|
>      next if hex_array.include?( inner_array[2] )
>      hex_array << inner_array[2]
>      .  .  .
>
> I wonder if there is a better way?  Any suggestions?

(1) auto-splat to avoid the [2] magic index

outer_array.each do |mtime, name, hexdigest|

(2) Use a hash, rather than an array, to record ones you've processed. 
This avoids a linear search on every iteration

seen = {}
outer_array.each do |mtime, name, hexdigest|
  next if seen[hexdigest]
  seen[hexdigest] = true
  ...
end

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