On Tue, Jan 6, 2009 at 3:07 PM, Mark Engelberg <mark.engelb...@gmail.com> wrote: > > 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.
Excellent suggestions! I spent many hours today rewriting my snake program to do this. The new version is at http://www.ociweb.com/mark/programming/ClojureSnake.html. It doesn't use any refs or transactions. Parts of it are greatly simplified over what I had before. For example, creation of the JPanel proxy is shorter. I only have one global remaining and can't figure out how to get rid of it. It is the key code of the last key pressed. That gets set in the keyPressed method of the JPanel which is a KeyListener. I know we're beating this into the ground, but feedback is still welcomed. If you see anything in the code that you would do differently, I'd be interested in hearing about it. -- 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 -~----------~----~----~----~------~----~------~--~---
