(Extracting these questions from my previous thread for clarity.) Below is my simplest possible program to solve the Fasta shootout benchmark. http://shootout.alioth.debian.org/gp4/benchmark.php?test=fasta&lang=all http://haskell.org/haskellwiki/Shootout/Fasta I can see one remaining flaw - the line marked 'Ugly'. What's the best way to get rid of this line? Any other suggestions for simplifying or improving the program would also be interesting. This code is about three or four times slower that the current fastest GHC entry for the Fasta benchmark. I'll elaborate it for speed when I've produced the best version regardless of speed. Richard. {-# OPTIONS -O -fexcess-precision #-} -- The Computer Language Shootout : Fasta -- http://shootout.alioth.debian.org/ -- Simple solution by Richard Kelsall. -- http://www.millstream.com/ import System main = do n <- getArgs >>= readIO . head title "ONE" "Homo sapiens alu" writeLined (cycle alu) (n * 2) title "TWO" "IUB ambiguity codes" let (r1, r2) = splitAt (fromIntegral (n * 3)) (rand 42) -- Ugly !! writeLined (map (look iubs) r1) (n * 3) title "THREE" "Homo sapiens frequency" writeLined (map (look homs) r2) (n * 5) title :: String -> String -> IO () title a b = putStrLn $ ">" ++ a ++ " " ++ b look :: [(Char, Float)] -> Float -> Char look [(c, _)] _ = c look ((c, f) : cfs) r = if r < f then c else look cfs (r - f) lineWidth = 60 writeLined :: [Char] -> Integer -> IO () writeLined cs 0 = return () writeLined cs n = do let w = min n lineWidth (cs1, cs2) = splitAt (fromInteger w) cs putStrLn cs1 writeLined cs2 (n - w) rand :: Int -> [Float] rand seed = newran : (rand newseed) where im = 139968 ia = 3877 ic = 29573 newseed = (seed * ia + ic) `rem` im newran = fromIntegral newseed / fromIntegral im alu = "GGCCGGGCGCGGTGGCTCACGCCTGTAATCCCAGCACTTTGGGAGGCCGAGGCGGGCGGA\ \TCACCTGAGGTCAGGAGTTCGAGACCAGCCTGGCCAACATGGTGAAACCCCGTCTCTACT\ \AAAAATACAAAAATTAGCCGGGCGTGGTGGCGCGCGCCTGTAATCCCAGCTACTCGGGAG\ \GCTGAGGCAGGAGAATCGCTTGAACCCGGGAGGCGGAGGTTGCAGTGAGCCGAGATCGCG\ \CCACTGCACTCCAGCCTGGGCGACAGAGCGAGACTCCGTCTCAAAAA" iubs = [('a', 0.27), ('c', 0.12), ('g', 0.12), ('t', 0.27), ('B', 0.02), ('D', 0.02), ('H', 0.02), ('K', 0.02), ('M', 0.02), ('N', 0.02), ('R', 0.02), ('S', 0.02), ('V', 0.02), ('W', 0.02), ('Y', 0.02)] homs = [('a', 0.3029549426680), ('c', 0.1979883004921), ('g', 0.1975473066391), ('t', 0.3015094502008)]