I got Hudak's Haskell School of Expression today and just tried a couple of the graphics programs from the software I downloaded at the book site. Both seem to hang on opening a window. Is there a fix for this problem? I'm on a Fedora 14 Linux (32-bit) box running GHC version 6.12.3. Michael ============ *SimpleGraphics> :l Snowflake.lhs [1 of 2] Compiling SOE ( SOE.hs, interpreted ) [2 of 2] Compiling Snowflake ( Snowflake.lhs, interpreted ) Ok, modules loaded: Snowflake, SOE. *Snowflake> main ============ This code was automatically extracted from a .lhs file that uses the following convention: -- lines beginning with ">" are executable -- lines beginning with "<" are in the text, but not necessarily executable -- lines beginning with "|" are also in the text, but are often just expressions or code fragments.
module Snowflake where import SOE m = 81 :: Int -- multiple of 3 for triangle size x = 250 :: Int -- x and y coordinates of y = 250 :: Int -- center of snowflake colors = [ Magenta, Blue, Green, Red, Yellow ] snowflake :: Window -> IO () snowflake w = do drawTri w x y m 0 False -- draw first triangle w/flat top flake w x y m 0 True -- begin recursion to complete job flake :: Window -> Int -> Int -> Int -> Int -> Bool -> IO () flake w x y m c o = do drawTri w x y m c o -- draw second triangle let c1 = (c+1)`mod`5 -- get next color if (m<=3) then return () -- if too small, we're done else do flake w (x-2*m) (y-m) (m`div`3) c1 True -- NW flake w (x+2*m) (y-m) (m`div`3) c1 True -- NE flake w x (y+2*m) (m`div`3) c1 True -- S flake w (x-2*m) (y+m) (m`div`3) c1 False -- SW flake w (x+2*m) (y+m) (m`div`3) c1 False -- SE flake w x (y-2*m) (m`div`3) c1 False -- N drawTri :: Window -> Int -> Int -> Int -> Int -> Bool -> IO () drawTri w x y m c o = let d = (3*m) `div` 2 ps = if o then [(x,y-3*m), (x-3*m,y+d), (x+3*m,y+d)] -- side at bottom else [ (x,y+3*m), (x-3*m,y-d), (x+3*m,y-d)] -- side at top in drawInWindow w (withColor (colors !! c) (polygon ps)) main = runGraphics ( do w <- openWindow "Snowflake Fractal" (500,500) drawInWindow w (withColor White (polygon [(0,0),(499,0),(499,499),(0,499)])) snowflake w spaceClose w ) spaceClose :: Window -> IO () spaceClose w = do k <- getKey w if k==' ' || k == '\x0' then closeWindow w else spaceClose w