compareStrings s1 s2 = 2.0 * fromIntegral i / fromIntegral u
    where
      i = length $ intersect pairs1 pairs2
      u = length pairs1 + length pairs2
      pairs1 = wordLetterPairs $ uppercase s1
      pairs2 = wordLetterPairs $ uppercase s2
compareStrings s1 s2 = 2.0 * fromIntegral i / fromIntegral u
    where
      i = length $ intersect pairs1 pairs2
      u = length pairs1 + length pairs2
      pairs1 = wordLetterPairs $ uppercase s1
      pairs2 = wordLetterPairs $ uppercase s2
compareStrings s1 s2 = 2.0 * fromIntegral i / fromIntegral u
    where
      i = length $ intersect pairs1 pairs2
      u = length pairs1 + length pairs2
      pairs1 = wordLetterPairs $ uppercase s1
      pairs2 = wordLetterPairs $ uppercase s2