On Wed, 18 Jun 2003 17:36:28 -0700
"Hal Daume"
Note that there is essentially no difference between f1 and f2. When you $! in f2, all it does is ensure that the argument isn't undefined. It doesn't evaluate any of the list. Try $!! from the DeepSeq module or write your own list-forcing function.
Thank you very much. I understand. However my original program still (or maybe from the beginning) stack-overflows at another point, in the middle of the evaluation of "forpaintbdry". Please give me some advice. ----------- -- snippet of the program for painting a random matrix from its boundary. module Main where import System import Random import Array import Ix import List main = putStrLn $ show $ forpaintbdry $ rmat 200 forpaintbdry m = [(pos, Live) | pos <- (uncurry bdryidxlist) $ bounds m , isUnknown $ m ! pos ] bdryidxlist :: (Int, Int) -> (Int, Int) -> [(Int, Int)] bdryidxlist (a1, a2) (b1, b2) = nub $ [(ab, j) | ab <- [a1, b1], j <- [a2..b2]] ++ [(i, ab) | ab <- [a2, b2], i <- [a1..b1]] rmat n = listArray ((1,1),(n,n)) $ map ct (randoms (mkStdGen 1) ::[Bool]) where ct True = Unknown ct False = Dead data CellColor = Live | Unknown | Dead isUnknown Unknown = True isUnknown _ = False instance Show CellColor where show Live = "Live" show Unknown = "Unknown" show Dead = "Dead"