-----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-----