Hi Zsolt, I recommend you to try haskell tutorials/books, like LYaHfGG [1] or RWH [2]. Same on OpenGL, RB [3]. preservingMatrix is wrapper of push/popMartix, which stores opengl transformation matrices in stack (see details in RB). [1] http://learnyouahaskell.com/chapters [2] http://book.realworldhaskell.org/read/ [3] http://www.opengl.org/documentation/red_book/ On Thu, Nov 26, 2009 at 8:37 PM, Zsolt Ero wrote:

Sorry to ask such a basic question here, but I am trying to write my first Haskell OpenGL animation and just encontered with thsese questions:

Could someone point me to some help on how does "do" work and how does preservingMatrix?

I am trying to write a program starting from the OpenGL tutorial on the wiki, but I never used do's before.

My very basic question is that how do I generally repeat a command many times? I understand "do" can do it, but it's not clear to me how to use it and how it works.

So if I would like to write the following in one line, how could I write it?: spiral 0.7 spiral 0.8 spiral 0.9 spiral 1.0

I don't understand in which cases I can use "map something [0.7,0.8..1]" and in which cases I need do and how could I map using do.

...

From the tutorial, I could write this line, which works, but I don't really know what does mapM_ and preservingMatrix do.

mapM_ (\x -> preservingMatrix $ do scale x x (1::GLfloat) rotate (x*(200)) $ Vector3 0 0 (1::GLfloat) spiral ((sin(a/50))^2/2+0.5) ) $ ([0.5,0.6..1::GLfloat])

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