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#!/usr/bin/env ruby

class Lexicon
  Pair = Struct.new(:token, :word)

  @lexicon = {
    'north' => :direction,
    'south' => :direction,
  }

  def self.scan(string)
    words = string.split
    words.map do |word|
      Pair.new(@lexicon[word], word) if @lexicon.key?(word)
    end
  end
end

p Lexicon.scan 'north' #=> [#<struct Lexicon::Pair token=:direction, word="north">]
p Lexicon.scan 'north south' #=> [#<struct Lexicon::Pair token=:direction, word="north">, #<struct Lexicon::Pair token=:direction, word="south">]