HaskellでOpenGL(GLUT)を使って、円を描画する。

2d-circle.hs

import Graphics.UI.GLUT

display :: DisplayCallback
display = do
    clear [ColorBuffer]
    color (Color3 0 0 0 :: Color3 GLdouble)
    renderPrimitive LineLoop $ mapM_ vertex2d [Vertex2 (0.5*cos t) (0.5*sin t) | t <- [0,0.01..2*pi]]
    flush
        where
            vertex2d = vertex :: Vertex2 GLdouble -> IO ()

main :: IO ()
main = do
    getArgsAndInitialize
    initialDisplayMode $= [RGBAMode]
    createWindow "Sample"
    clearColor $= Color4 1 1 1 1
    displayCallback $= display
    mainLoop