create ngrams in ruby

ngram.rb

# Source https://snippets.aktagon.com/snippets/584-generating-word-n-grams-with-ruby
module Ngram
  REGEX = /\w+/
  def ngram_tokenize
     self.downcase.scan(REGEX)
  end

  def ngram(n=1)
    res = Set.new
    words = ngram_tokenize
    word_count = words.length
    words.each_with_index do |word, ix|
      min = ix
      max = ix + (n-1)
      break if word_count <= max
      res.add words[min..max].join(' ')
    end
    res
  end

  def ngrams(range=1..3)
    return ngram(range) if range.is_a?(Fixnum)
    res = Set.new
    range.each do |n|
      res.merge ngram(n)
    end
    res
  end
end

class String
  include Ngram
end

https://snippets.aktagon.com/snippets/584-generating-word-n-grams-with-ruby