[Haskell-cafe] Infinite grid

Martijn van Steenbergen martijn at van.steenbergen.nl
Fri Jan 2 11:44:59 EST 2009

Henning Thielemann wrote:
> A dungeon game? :-)

Yes. :-)

Thank you all for your answers! I especially like David's 
no-intermediate-structure solution because it allows for defining the 
area in terms of neighbours instead of needing an index on the rooms.

Now that I have core functionality in my game I want to try and build 
some interesting areas, such as infinite ones: a infinite grid, or an 
N-dimensional Hilbert curve. Because rooms are mutable, I am building 
them inside a state monad and use ids:

mkRoom :: M RoomId
addExit :: RoomId -> Exit -> M ()
type Exit = (String, RoomId)

I thought my original question would give me some ideas on how to 
construct infinite areas, but this monadic interface complicates things 
somewhat. If I create all rooms at once, runState never returns, so I 
will have to create them lazily, perhaps by changing:

type Exit = M (String, RoomId)

But I think in addition to that I will also needs refs, so that the 
monadic computation can check using a ref whether it's created its 
target room before.

I will have to experiment and think on this some more.


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