Question

Every time I try to compile and run a tutorial that I have found, I get a message saying either “Could not find module GL” or “Could not find module GLUT.” I have tried replacing “import GLUT” with “import Graphics.Rendering.OpenGL” and “import Graphics.UI.GLUT”, but this just causes even more errors. Should “import GLUT” do something, or is it just pseudo code that I’m misinterpreting?

Answer 1

GLUT and OpenGL are both needed to run an OpenGL application. This isn’t C where importing one will import the other.

So, you need to import the libraries like this:

import Graphics.Rendering.OpenGL
import Graphics.UI.GLUT

The following code will then create a simple OpenGL window that simply flushes the command buffer on each render, to check if the program works:

main :: IO ()
main = do 
  (progname, _) <- getArgsAndInitialize
  createWindow "Hello World"
  displayCallback $= flush
  mainLoop

Compile the program with:

ghc --make program.hs

If this doesn’t succeed, it means that you didn’t install the Haskell Platform correctly, and you need to check that the OpenGL packages are correctly installed.