[rules-dev] pacman
For anyone interested i just did an initial commit for the rudementary
implementation parts for a Pacman game. Loads a Grid and a Character
into the working memory and listens to the arrow keys to move the
Character around (text output only). It only accepts valid directions
and the Character cannot move off the grid, and score is updated as it
eats Food.
It also demostrates entry and exit points. For instance this rule has
it's "KeyListener" entry point hooked up to a KeyListener impl that
inserts KeyEvents. From the KeyEvent it creates a Derived (not in
working memory) possible Direction, validates that Direction. If valid
the old Direction is retracted and the new one inserted. I use the
exitpoint to send print information to a channel, which is appended to
the GUI.
/**
* Detects a new keypress (release). Creates derived possible Direction
and validates it.
* If the Direction is valid, delete the old Direction and replace with
the new one.
*/
rule keyListenerRule dialect "mvel" when
$keyEvent : KeyEvent() from entry-point "KeyListener"
$l : Location()
$newD : Direction() from createDirection( $l.character, $keyEvent )
$target : Cell( row == ($l.row + $newD.vertical), col == ($l.col +
$newD.horizontal) )
CellContents( cell == $target, cellType != CellType.WALL )
$oldD : Direction( character == $l.character )
then
exitPoints["ConsoleExitPoint" ].insert( "insert " + $newD +
"\n" );
retract( $keyEvent );
retract( $oldD );
insert( $newD );
end
As the Tick, simulated time, increases we attempt to change it's
Location based on the given Direction. We make sure the new Location is
valid, and if so schedule the new Location, in time with the Tick.
/**
* Checks that the current Direction moves to a valid location, i.e. not
a WALL.
* It does not set the new direction straight away, this is because we
need movement to be intime
* with the Tick increase, so we schedule the new Location instead.
*/
rule validDirection dialect "mvel" when
$l : Location( )
$d : Direction( character == $l.character )
$target : Cell( row == ($l.row + $d.vertical), col == ($l.col +
$d.horizontal) )
CellContents( cell == $target, cellType != CellType.WALL )
not ScheduledLocationUpdate( location == $l )
$t : Tick()
then
insert( new ScheduledLocationUpdate($l, $l.row += $d.vertical,
$l.col += $d.horizontal, $t.tock + 1) );
end
/**
* When the Tick increases, update any Locations from inserted scheduled
updates.
*/
rule setNewDirection dialect "mvel" when
$s : ScheduledLocationUpdate()
$l : Location( this == $s.location )
Tick( tock == $s.tock )
then
exitPoints["ConsoleExitPoint"].insert( "set new Location " + $l +
"\n" );
modify( $l ) { row = $s.row, col = $s.col };
retract( $s );
end
Notice the whole thing id driven relationally, because everything is
linked relationally we can exploit that to drive the engine
declaratively with only a few rules.
I've committed everything to drools-examples for now, you'll need drools
trunk, as there are a few fixes necessary for this to work:
http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples...
http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples...
http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples...
The grid1.dat holds the grid layout, it's a declarative symbol layout,
trivial to change to explore new grids.
It's still very basic. Next I want to work on variable speed for
characters, then I'll start to add Monsters and power pellets. Once we
have the full backend working, the idea is to hook it up to an existing
pacman gui such as SwtPacman. SwtPacman source code is available here:
http://www.jboss.org/community/wiki/pacman
I'll probably blog this later, as a few more bits are added. But
hopefully this will start to demonstrate to people some more complex
problems, and also help drive the drools team on how to improve our
language and engine.
Mark