[Haskell-beginners] Optimise mininal date conversion function?

Hi, I have this crude function that converts a date in YYYY/MM/DD format to an Int, but it's slow. Does any one have a clue on how to optimize it? date2int :: B.ByteString -> Int date2int b = y*12*31 + (m-1)*31 + (d-1) where y = read . B.unpack . B.take 4 $ b m = read . B.unpack . B.take 2 . B.drop 5 $ b d = read . B.unpack . B.drop 8 $ b Here is the original C++ function that was ported: static unsigned date2int (const char *date){ return atoi(date)*12*31+(atoi(date+5)-1)*31+atoi(date+8)-1; } Thanks, Patrick -- ===================== Patrick LeBoutillier Rosemère, Québec, Canada