On Thu, Jan 8, 2009 at 5:08 AM, Tom Ayerst <tom.aye...@gmail.com> wrote: > Hi Mark, > > I don't think this approach works in Clojure / Swing, but I may be > mistaken, I often am. > > The issue is the event thread. In Abhishek's original and it's derivatives > the Swing event thread is used and the timer pushes events into it so key > press events and the game timer run in the same thread. This allowed Stuart > to pass the game into the function containing the JPanel proxy and for > everything to live in the Swing event thread (which is hidden from the > application). In fact the code should be safe without concurrency > constructs. > > Using loop - recur means there are now two threads in the code (The app loop > and Swing event loop) and these must be coordinated. This is, I think, why > Mark needed that last global and Stuart didn't.
My latest code no longer has any globals. See the atom named key-code-atom at http://www.ociweb.com/mark/programming/ClojureSnake.html. > I don't think there is a way to do this without some mutation because of the > implementation of Swing, but, as I said, I may be wrong. There will need to > be at least one concurrency construct. The code at that URL does work. I haven't been able to think of a scenario where it might fail, despite the fact that I'm painting outside the event dispatch thread (EDT). However, if there's a better way to do this, I'm all ears! > 2009/1/6 Mark Engelberg <mark.engelb...@gmail.com> >> >> One way to approach this without mutation is as follows: >> >> Decide on a data representation that represents the entire state of >> the game world at a given instant. >> >> Write a function which can draw this state. >> Write a function which takes the state and player keypresses as input, >> and returns a new updated state. >> Write a function which takes the state and returns the new state just >> from time elapsing. >> >> Note that none of the above functions mutate anything. It's all about >> returning fresh states, which fits well with Clojure's standard >> handling of data structures. >> >> Then write a loop that consumes an initial state, and creates a game >> experience by repeatedly applying the above functions. No globals or >> refs are required, just keep passing the new states back into the loop >> for further processing. >> >> This is an outline of the strategy employed by the "world" teachpack >> that accompanies the "How to Design Programs" curriculum that uses PLT >> Scheme. Students routinely develop the snake program as a homework >> assignment, using this approach. -- R. Mark Volkmann Object Computing, Inc. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
