Sorry, I forgot the attachment earlier. Daniel
-- | Build up random strings for use in a wc stress test.
module Main where
import Control.Monad
import Data.Array
import Data.List
import System.Environment
import System.IO
import System.Random
listToArray lst = listArray (0, length lst - 1) lst
lineChars = listToArray $ ['a'..'z'] ++ ['A' .. 'Z'] ++ (replicate 10 ' ')
randomLineLength = 40
-- | Generate a vaguely random list that's definitely
-- lazy, without calling randomRs.
scramble lower upper | upper < lower = scramble upper lower
| otherwise = map (+lower) $ scramble' 0 1
where scramble' n m = (n `mod` spread):scramble' m (n + m)
spread = upper - lower + 1
-- | Maybe the problem is that randomRs is a separate function?
iterRandom lower upper g = let (x, g') = randomR (lower, upper) g in
x:(iterRandom lower upper g)
randomLines g =
map fst $ tail $ splitPairs
where splitPairs = scanl (flip ($) . snd) ([], toSplit) splitters
toSplit = {-# SCC "toSplit" #-} map (lineChars!) $ randomRs (bounds lineChars) g
--toSplit = {-# SCC "toSplit" #-} map (lineChars!) $ (uncurry iterRandom) (bounds lineChars) g
--toSplit = {-# SCC "toSplit" #-} map (lineChars!) $ uncurry scramble $ bounds lineChars
--toSplit = {-# SCC "toSplit" #-} map (lineChars!) $ unfoldr (Just . randomR (bounds lineChars)) g
splitters = map splitAt splitPoints
splitPoints = randomRs ((randomLineLength * 3) `div` 4,
(randomLineLength * 5) `div` 4) g2
(g1, g2) = split g
-- | Chop a list up into pieces of (at most) a given length.
segment :: Int -> [a] -> [[a]]
segment n = unfoldr (doSplit n)
where doSplit n [] = Nothing
doSplit n lst = Just $ splitAt n lst
main = do g <- getStdGen
a <- getArgs
when (length a > 1)
(print "Too many arguments")
let count = if null a then 10 else read $ head a
output = unlines $ take count $ randomLines g
putStr output
-- This doesn't take more or less heap, so putStr
-- must be doing something similarly lazy.
--sequence_ $ map putStr $ segment 60000 output
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