improved_fizzbuzz.rb

def fizzbuzz(start, final)
  start.upto(final) do |i|
    puts fizzbrain(i)
  end
end

def fizzbrain(num)
  output = ''
  output << 'Fizz' if num % 3 == 0
  output << 'Buzz' if num % 5 == 0
  output << 'Blah' if num % 7 == 0
  output.empty? ? num : output
end

fizzbuzz(1, 10)

reverse_string.rb

input = "The cat is blue"

def reverse_sentence(input)
  # break sentence into list of
  # words
  list_of_words = input.split(' ')


  # reverese list of words
  list_of_words = list_of_words.reverse

  # convert list of words into
  # a sentence
  list_of_words.join(' ')
end

puts reverse_sentence(input)

string_concat_recursion.rb

x = ['The', 'cat', 'is', 'blue.']

def recur_concat(input, result)
  if input.empty?
    return result
  else
    return recur_concat(
      input[1..-1],
      result + "#{input[0]} "
    )
  end
end

puts recur_concat(x, '')