Re: [Haskell-cafe] Sometimes I wish there was a global variable
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Rafael Cunha de Almeida wrote: | Hello, | | I am writing a OpenGL program in haskell, it can be found in: | http://github.com/aflag/galo/tree/master | But I hope this e-mail will be self-contained :). | | My main function goes like this: | (...) | rotX - newIORef (0.0::GLfloat) | rotY - newIORef (0.0::GLfloat) | pos - newIORef (0.0::GLfloat, 0.0, 0.0) | | displayCallback $= display (map f range) rotX rotY pos | | keyboardMouseCallback $= Just (keyboardMouse rotX rotY pos) | (...) | | Notice that rotX, rotY and pos are meant to be used as comunication | between the keyboardMouse and display functions. They need to be set as | 0 first, so display won't do anything. Only when they user press a few | buttons that those values change, so display behaves accordanly. | | In a state-based language I would place display and keyboardMouse in one | module and let them communcate to each other like they want. In haskell, | I'm not quite sure how to do it except by that parameter passing style. | | I thought about how state-monad may help with that. But I'm not sure how | I'd make the state variable to be contained inside a | display/keyboardMouse module. Another way to do this would be something like this: ~main = do ~ ... ~ displayCallback $= initialDisplayFunction ~ keyboardMouseCallback $= keyboardMouseFunction ~ ... ~keyboardMouseFunction = do ~ rotX - ... ~ rotY - ... ~ pos - ... ~ ... ~ displayCallback $= display ... rotX rotY rotZ You could even write your own state monad that does this callback reassignment for you (perhaps by wrapping StateT s IO a), then you can forget about all this explicit parameter passing. - - Jake -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAknHq+kACgkQye5hVyvIUKnX3ACeMLD8FLOTEya8can6veyp6cT3 ClMAnRdfl/DyOshvzlBF8QCtYgTf87fd =Bp4F -END PGP SIGNATURE- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Sometimes I wish there was a global variable
Hello, I am writing a OpenGL program in haskell, it can be found in: http://github.com/aflag/galo/tree/master But I hope this e-mail will be self-contained :). My main function goes like this: (...) rotX - newIORef (0.0::GLfloat) rotY - newIORef (0.0::GLfloat) pos - newIORef (0.0::GLfloat, 0.0, 0.0) displayCallback $= display (map f range) rotX rotY pos keyboardMouseCallback $= Just (keyboardMouse rotX rotY pos) (...) Notice that rotX, rotY and pos are meant to be used as comunication between the keyboardMouse and display functions. They need to be set as 0 first, so display won't do anything. Only when they user press a few buttons that those values change, so display behaves accordanly. In a state-based language I would place display and keyboardMouse in one module and let them communcate to each other like they want. In haskell, I'm not quite sure how to do it except by that parameter passing style. I thought about how state-monad may help with that. But I'm not sure how I'd make the state variable to be contained inside a display/keyboardMouse module. []'s Rafael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Sometimes I wish there was a global variable
Rafael Cunha de Almeida almeida...@gmail.com writes:
My main function goes like this:
(...)
rotX - newIORef (0.0::GLfloat)
rotY - newIORef (0.0::GLfloat)
pos - newIORef (0.0::GLfloat, 0.0, 0.0)
displayCallback $= display (map f range) rotX rotY pos
keyboardMouseCallback $= Just (keyboardMouse rotX rotY pos)
(...)
...
In a state-based language I would place display and keyboardMouse in one
module and let them communcate to each other like they want. In haskell,
I'm not quite sure how to do it except by that parameter passing style.
You could try something like this: (and apologies in advance for any
typoes)
import Control.Concurrent.MVar
data MyState = MyState {
rotX :: GLFloat
, rotY :: GLFloat
, pos :: (GLFloat,GLFloat)
}
myDisplayCallback :: MVar MyState - IO ()
myDisplayCallback =
flip modifyMVar_ $ \(MyState rx ry p) - do
(newRx, newRy, newP) - yourCodeGoesHere
return $ MyState newRx newRy newP
main = do
mvar - newMVar $ MyState 0 0 (0,0)
displayCallback $= myDisplayCallback mvar
...
Cheers,
G.
--
Gregory Collins g...@gregorycollins.net
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