From: "Jesús Gabriel y Galán" <jgabrielygalan@...>
Date: 2009-02-03T00:44:19+09:00
Subject: Re: Quicker finding strings? Alternative for array, hash, set?

On Mon, Feb 2, 2009 at 3:37 PM, Patrick Put <patrick.put@gmail.com> wrote:
>> If you do not want to attach information to those words then a Set is
>> more appropriate: same O(1) lookup but no key value mapping.
> Is the implementation "under the hood" the same? That would mean my
> choice to use a Set was not so bad after all.

If you check here:

http://www.ruby-doc.org/core/classes/Set.html

you can see the source code for each method. For example this is the method new:

# File lib/set.rb, line 64
  def initialize(enum = nil, &block) # :yields: o
    @hash ||= Hash.new

    enum.nil? and return

    if block
      enum.each { |o| add(block[o]) }
    else
      merge(enum)
    end
  end

So you can see, it uses a Hash underneath. Let's take a look at the add method:

# File lib/set.rb, line 195
  def add(o)
    @hash[o] = true
    self
  end

So, it's using a hash with true as the values (the same I did in my
example). Of course, if the true doesn't mean anything to you (which
shouldn't as you are not using the values), using a Set is a bit more
clear, and has convenience methods for Set "arithmetic".

Jesus.