test.rb

#! /usr/env/bin/ruby

# Convert a string into an array of arrays with the word and number
# of occurances of that word.
#
# @param [text] : String
# @return [array] : [[word, count], [word2, count2]]
def analyze_paragraph(text)
  # we don't need anything except spaces and lower case letters
  text = text.to_s.downcase.gsub(/[^0-9A-Za-z\s]/, '')

  # use a hash as it has better performance, and easily converts
  # to an array of arrays
  array_of_words = Hash.new
  text.split(" ")
      .uniq
      .each { |word| array_of_words[word] = text.scan(word).length }

  return array_of_words.to_a
end

p analyze_paragraph("To be, or not to be.")
p analyze_paragraph("Hello World!")
p analyze_paragraph(1)
p analyze_paragraph("")
p analyze_paragraph(:symbol)