def convert_temp(temp, input_scale: String, output_scale: 'celsius')
  conversion = [
    input_scale.strip.downcase.to_sym,
    output_scale.strip.downcase.to_sym
  ]
  k_to_c = lambda { |k| k - 273.15 }
  c_to_k = lambda { |c| c + 273.15 }
  c_to_f = lambda { |c| (c * (9.0/5.0)) + 32.0 }
  f_to_c = lambda { |f| (f - 32.0) * (5.0/9.0) }

  case conversion
    when [:kelvin, :kelvin]
      temp
    when [:celsius, :celsius]
      temp
    when [:fahrenheit, :fahrenheit]
      temp
    when [:kelvin, :celsius]
      k_to_c.call(temp)
    when [:celsius, :kelvin]
      c_to_k.call(temp)
    when [:kelvin, :fahrenheit]
      c_to_f.call(k_to_c.call(temp))
    when [:fahrenheit, :kelvin]
      c_to_k.call(f_to_c.call(temp))
    when [:celsius, :fahrenheit]
      c_to_f.call(temp)
    when [:fahrenheit, :celsius]
      f_to_c.call(temp)
    else
      raise StandardError, "Invalid Units: #{input_scale} or #{output_scale}"
  end
end