On Mon, Apr 30, 2007 at 11:16:47PM +0200, Denis Volk wrote:
Hello all,
I am trying to make a (turn-based) game in Haskell and need to pass around quite a bit of information, so using the State monad seems most appropriate. My question is, which is a better idea:
1) Using State GameState r and then call execState for each game event (i.e. user input) so I can do IO 2) Using StateT GameState IO () and have the entire game live in one big execStateT call. (I note XMonad does something similar.)
There are difficulties with the first option, including keeping even more state about what we're doing (for instance, are we in a menu?), and adding stuff later would possibly require substantial rewrites. Other than the fact that I would have IO in places where it perhaps shouldn't be, the second option seems better, but I am new to all this and it may be that I'm missing something.
You can also give some of your actions the type Monad m => StateT GameState m (), so that parametricity guarantees no actual IO will occur. Stefan