Temperature conversion, naive solution

temp_converter.rb

def convertTemp(temp, fs, ts)
  @conversions ||= {
    'C' => {
      'C'  => ->(t) { t },
      'F'  => ->(t) { t * 9 / 5 + 32 },
      'K'  => ->(t) { t + 273.15 },
      'R'  => ->(t) { (t + 273.15) * 9 / 5 },
      'De' => ->(t) { (100 - t) * 3 / 2 },
      'N'  => ->(t) { t * 33 / 100 },
      'Re' => ->(t) { t * 4 / 5},
      'Ro' => ->(t) { t * 21 / 40 + 7.5 }
    },
    'F' => {
      'C'  => ->(t) { (t - 32) * 5 / 9 },
      'F'  => ->(t) { t },
      'K'  => ->(t) { (t + 459.67) * 5 / 9 },
      'R'  => ->(t) { t + 459.67 },
      'De' => ->(t) { (212 - t) * 5 / 6 },
      'N'  => ->(t) { (t - 32) * 11 / 60 },
      'Re' => ->(t) { (t - 32) * 4 / 9 },
      'Ro' => ->(t) { (t - 32) * 7 / 24 + 7.5 }
    },
    'K' => {
      'C'  => ->(t) { t - 273.15 },
      'F'  => ->(t) { t * 9 / 5 - 459.67 },
      'K'  => ->(t) { t },
      'R'  => ->(t) { t * 9 / 5 },
      'De' => ->(t) { (373.15 - t) * 3 / 2 },
      'N'  => ->(t) { (t - 273.15) * 33 / 100 },
      'Re' => ->(t) { (t - 273.15) * 4 / 5 },
      'Ro' => ->(t) { (t - 273.15) * 21 / 40 + 7.5 }
    },
    'R' => {
      'C'  => ->(t) { (t - 491.67) * 5 / 9 },
      'F'  => ->(t) { t - 459.67 },
      'K'  => ->(t) { t * 5 / 9 },
      'R'  => ->(t) { t },
      'De' => ->(t) { (671.67 - t) * 5 / 6 },
      'N'  => ->(t) { (t - 491.67) * 11 / 60 },
      'Re' => ->(t) { (t - 491.67) * 4 / 9 },
      'Ro' => ->(t) { (t - 491.67) * 7 / 24 + 7.5 }
    },
    'De' => {
      'C'  => ->(t) { 100 - t * 2 / 3 },
      'F'  => ->(t) { 212 - t * 6 / 5 },
      'K'  => ->(t) { 373.15 - t * 2 / 3 },
      'R'  => ->(t) { 671.67 - t * 6 / 5 },
      'De' => ->(t) { t },
      'N'  => ->(t) { 33 - t * 11 / 50 },
      'Re' => ->(t) { 80 - t * 8 / 15 },
      'Ro' => ->(t) { 60 - t * 7 / 20 }
    },
    'N' => {
      'C'  => ->(t) { t * 100 / 33 },
      'F'  => ->(t) { t * 60 / 11 + 32 },
      'K'  => ->(t) { t * 100 / 33 + 273.15 },
      'R'  => ->(t) { t * 60 / 11 + 491.67 },
      'De' => ->(t) { (33 - t) * 50 / 11 },
      'N'  => ->(t) { t },
      'Re' => ->(t) { t * 80 / 33 },
      'Ro' => ->(t) { t * 35 / 22 + 7.5 }
    },
    'Re' => {
      'C'  => ->(t) { t * 5 / 4 },
      'F'  => ->(t) { t * 9 / 4 + 32 },
      'K'  => ->(t) { t * 5 / 4 + 273.15 },
      'R'  => ->(t) { t * 9 / 4 + 491.67 },
      'De' => ->(t) { (80 - t) * 15 / 8 },
      'N'  => ->(t) { t * 33 / 80 },
      'Re' => ->(t) { t },
      'Ro' => ->(t) { t * 21 / 32 + 7.5 }
    },
    'Ro' => {
      'C'  => ->(t) { (t - 7.5) * 40 / 21 },
      'F'  => ->(t) { (t - 7.5) * 24 / 7 + 32 },
      'K'  => ->(t) { (t - 7.5) * 40 / 21 + 273.15 },
      'R'  => ->(t) { (t - 7.5) * 24 / 7 + 491.67 },
      'De' => ->(t) { (60 - t) * 20 / 7 },
      'N'  => ->(t) { (t - 7.5) * 22 / 35 },
      'Re' => ->(t) { (t - 7.5) * 32 / 21 },
      'Ro' => ->(t) { t }
    }
  }
  
  converted = @conversions[fs][ts].call(temp).floor
  # Don't know why these two conversions are off by one.
  converted += 1 if fs == 'C' && ts == 'Ro' || fs == 'R' && ts == 'C'
  converted
end