Re: some help on do and preservingMatrix

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 <[email protected]> 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])
>
> Zsolt
> _______________________________________________
> HOpenGL mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/hopengl
>



-- 
BR,
Stanislav `Cfr` Serebryakov,
http://claimid.com/cfr.

       ,-""-.
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     | () )   |<_.-.
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       `-..-'      `-  hjw

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