[Haskell-beginners] State Monads (and OpenGL)
tvhobbs at googlemail.com
Fri Nov 5 11:55:08 EDT 2010
I have a program which implements Conway's Game Of Life. It even has
an open GL UI which shockingly works.
I've followed a tutorial
which tells how to get the open GL to animate, and according to my
sysouts, that's working to. The problem I have comes with the fact
that between every frame I want to evolve my world but I'm really
struggling working out how to get the state stuff working.
Here's a snippet of my main function;
main = do
world <- sequence (take (worldSize * worldSize) $ repeat rand) --
randomly generate a square world
-- code snipped out
displayCallback $= (display position world) -- display method which
is called on every frame redraw
Here, world is a [Int] and represents my cells. The display function
as referenced by "displayCallback" is the function that is called back
to everytime the frame is redrawn.
I also have another function which takes in a world, updates the state
of the cells and the evolved world, thus;
evolve :: [Int] -> [Int]
I've been reading through (a lot of) tutorials on the state monad but
I'm not any closer to working out how I make the call to display take
some kind of updated world.
I've also got the following code;
type World = State [Int]
evolveS :: World [Int]
evolveS = do
w <- get
let w2 = evolve w
Which I believe to be the correct code for wrapping my [Int] in the
state monad but now I have two problems;
1) I don't know if it's correct
2) I don't know how to apply it, even if it is
Can anyone offer any advice?
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