[Haskell-cafe] Code from Haskell School of Expression hanging.

[michael rice]

That worked, though not sure why I had to delete the .o file.

On to ghci?

Michael

--- On Sun, 1/30/11, Paul L <ninegua at gmail.com> wrote:

From: Paul L <ninegua at gmail.com>
Subject: Re: [Haskell-cafe] Code from Haskell School of Expression hanging.
To: "michael rice" <nowgate at yahoo.com>
Cc: haskell-cafe at haskell.org, "Daniel Fischer" <daniel.is.fischer at googlemail.com>
Date: Sunday, January 30, 2011, 7:31 PM

Maybe you want to remove Snowflake.o (or even *.o) and then try compiling it again.
Regards,Paul Liu

On Sun, Jan 30, 2011 at 4:11 PM, michael rice <nowgate at yahoo.com> wrote:

SimpleGraphics has a bunch of main programs: main0, main1, main2, main3, and main3book. I sequentially changed each to main and ran all five successfully.


Then I did the same for Snowflake.lhs (see code below) which already had a single main function.

Michael

==============

[michael at localhost src]$ ghc --make Snowflake -main-is Snowflake
Linking Snowflake ...

/usr/lib/ghc-6.12.3/libHSrtsmain.a(Main.o): In function `main':
(.text+0x10): undefined reference to `ZCMain_main_closure'
/usr/lib/ghc-6.12.3/libHSrtsmain.a(Main.o): In function `main':
(.text+0x18): undefined reference to `__stginit_ZCMain'

collect2: ld returned 1 exit status
[michael at localhost src]$

==============

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

 
 
--- On Sun, 1/30/11, Daniel Fischer <daniel.is.fischer at googlemail.com> wrote:


From: Daniel Fischer <daniel.is.fischer at googlemail.com>
Subject: Re: [Haskell-cafe] Code from Haskell School of Expression hanging.

To: haskell-cafe at haskell.org,
 "michael rice" <nowgate at yahoo.com>
Date: Sunday, January 30, 2011, 6:48 PM

On Monday 31 January 2011 00:27:41, michael rice wrote:

> And here's the same with GHC. It never gets to linking and creating an
> executable the way the GLFW sample program does.
>
> Michael
>
> ===============
>
> [michael at localhost ~]$ cd ./SOE/SOE/src

> [michael at localhost src]$ ghc --make SimpleGraphics.lhs
> [2 of 2] Compiling SimpleGraphics   ( SimpleGraphics.lhs,
> SimpleGraphics.o ) [michael at localhost src]$

The module name is not Main, so to get an executable, you have to tell ghc 

what the Main module is.
Assuming SimpleGraphics.lhs contains a main function,

$ ghc --make SimpleGraphics -main-is SimpleGraphics

should do it.

Cheers,
Daniel












      
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-- 
Regards,
Paul Liu






      
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