Code  edit

#-----------------------------------------------------------------------
# TITLE:
#      life.tcl
#
# AUTHOR:
#      Will Duquette
#
# DESCRIPTION:
#      life.tcl implements John Conway's classic Game of Life, one of
#      the first experiments with what's now called artificial life.
#
#      Think of a plane divided up into squares like a checker board.
#      Each square can hold a one-celled animal.  You start the game
#      by placing cells in squares.  Then you watch the cells breed
#      and die through successive generations.  The game is to find
#      starting patterns that do interesting things.
#
#      Each square on the board has 8 neighbor squares; cells breed
#      and die based on how crowded they are, i.e., the number of
#      neighbors they have.  Each new generation is computed as
#      follows:
#
#      For each square, count the number of neighbor cells.
#      If the square is empty, and it has exactly 3 neighbor cells, a
#      new cell will be born there.  If the square has a cell in it,
#      and the cell has less than 2 or more than 3 neighbor cells,
#      the cell will die.  All of the counting is done first, and
#      then the new cells are added and the dead cell are removed all
#      at once.
#
#      This GUI implementation allows cells to be added and removed
#      by clicking on the board.  A generation passes when the
#      "Generate" button is clicked, or when the player presses the
#      Return key.
#
#      The implementation has two pieces: 
#
#      1.  The board, which contains cells that can be turned on
#          and off and knows how to compute a new generation.  The board
#          includes its own GUI display code.
#
#       2.  The rest of the GUI.
#
#      If the code were written for reuse, the board would be split into
#      two pieces: a generic gameboard suitable for Life, Othello, and
#      similar games, and Life code that uses the board.

if {![catch {
   package require snit 2-
}]} then {
   # We've got snit 2 (based on ensembles and whatsnot)
} elseif {![catch {
   package require snit 1
}]} then {
   # We're using snit 1.x
} else {
   # Won't work with less than 0.8
   package require snit 0.8
}

#-----------------------------------------------------------------------
# The Board
#
# The Board is implemented as a Tk canvas widget, broken up into
# squares on an NxN grid.  The background is white and the grid
# lines are cyan.  Each square holds a circle object which
# can be set to any desired color, normally white (for dead cells) and
# forestgreen (for living cells).  Each circle has a tag "i,j" so that
# it can be manipulated individually.

snit::widgetadaptor board {
   # This is still a canvas; delegate other methods and options to it:
   delegate method * to hull
   delegate option * to hull

   # By default, 20x20 cells
   option -cells 20
   # By default, each cell is 20x20 pixels
   option -pixels 20

   # Milliseconds between generations
   option -delay 200

   # For each cell on the board, this array remembers
   # whether the cell is alive or dead, and the coordinates of its 
   # neighbors; this allows the neighbors to be counted more quickly.
   variable data

   # Remembers the list of i,j indices, to save time while generating.
   variable indices {}

   # True if we're completely constructed, false otherwise.
   variable constructed 0

   constructor {args} {
       # FIRST, create the canvas.  Then configure the options.
       installhull [canvas $self -background white]
       $self configurelist $args

       # NEXT, set up the board.
       $self SetupBoard

       # No longer constructing.
       set constructed 1
   }

   onconfigure -cells {value} {
       set options(-cells) $value
       if {$constructed} {
           $self SetupBoard
       }
   }

   onconfigure -pixels {value} {
       set options(-pixels) $value
       if {$constructed} {
           $self SetupBoard
       }
   }

   method SetupBoard {} {
       # Destroy any previous definition
       $self delete all
       array unset data
       set cells $options(-cells)
       set pixels $options(-pixels)
       set size [expr {$cells * $pixels}]

       # FIRST, set the size of the canvas
       $hull configure -width $size -height $size

       # NEXT, draw the grid lines.
       for {set i 1} {$i < $cells} {incr i 1} {
           set pos [expr {$i * $pixels}]

           # Draw a vertical line $i cells over
           $hull create line 0 $pos $size $pos -fill cyan

           # Draw a horizontal line $i cells down
           $hull create line $pos 0 $pos $size -fill cyan
       }

       # NEXT, compute the list of indices
       set indices {}
       for {set i 0} {$i < $cells} {incr i 1} {
           for {set j 0} {$j < $cells} {incr j 1} {
               lappend indices $i,$j
           }
       }

       # NEXT, add a circle object to each cell
       for {set i 0} {$i < $cells} {incr i 1} {
           for {set j 0} {$j < $cells} {incr j 1} {
               # Compute the upper left corner of the circle
               set p0 [expr {$i*$pixels + 1}]
               set q0 [expr {$j*$pixels + 1}]

               # Compute the lower left corner of the circle
               set p1 [expr {$p0 + $pixels - 2}]
               set q1 [expr {$q0 + $pixels - 2}]

               # Create the circle, tagging it $i,$j
               $hull create oval $p0 $q0 $p1 $q1 \
                   -tag $i,$j -fill white -outline white

               # When the user clicks on it, it should toggle.
               $hull bind $i,$j <Button> [list $win toggle $i,$j]

               # Initialize the corresponding data structure
               set data($i,$j) 0

               # Cache the coordinates of each neighbor.
               set data($i,$j-neighbors) ""
               foreach {iof jof} {-1 -1  -1 0  -1 1  0 -1  
                   0 1  1 -1  1 0  1 1} {
                   set r [expr {($i + $iof) % $cells}]
                   set c [expr {($j + $jof) % $cells}]
                   lappend data($i,$j-neighbors) "$r,$c"
               }
           }
       }
   }

   # toggle ij
   #
   # Toggles cell i,j on the board.

   method toggle {ij} {
       # FIRST, toggle the cell in the array.
       if {$data($ij) == 0} {
           $self setcell $ij
       } else { 
           $self clearcell $ij
       }
   }

   # setcell ij
   #
   # Sets cell ij to alive
   method setcell {ij} {
       $hull itemconfigure $ij -fill forestgreen
       set data($ij) 1
   }

   # clearcell ij
   #
   # Clears (kills) cell i,j
   method clearcell {ij} {
       $hull itemconfigure $ij -fill white
       set data($ij) 0
   }

   # clear
   #
   # Sets the board cells to all dead
   method clear {} {
       foreach ij $indices {
           if {$data($ij)} {
               $self clearcell $ij
           }
       }
   }

   # generate
   #
   # The generate function takes the cells on the board through one 
   # generation.
   method generate {} {
       # Count the neighbors of each cell.  During start up we cached the
       # coordinates of the neighbors of each cell, so now we can just
       # iterate over them quickly.
       foreach ij $indices {
           set nCount 0

           foreach neighbor $data($ij-neighbors) {
               incr nCount $data($neighbor)
           }

           set count($ij) $nCount
       }

       # Set the new contents of each cell based on the count.
       set changes 0
       foreach ij $indices {
           if {$count($ij) < 2 || $count($ij) > 3} {
               if {$data($ij)} {
                   # Cell is dead
                   $self clearcell $ij
                   incr changes
               }
           } elseif {$count($ij) == 3} {
               # Cell is born, if there wasn't one
               if {!$data($ij)} {
                   $self setcell $ij
                   incr changes
               }
           }
       }

       return $changes
   }

   # run
   # 
   # Generate indefinitely.
   method run {} {
       if {[$self generate] > 0} {
           after $options(-delay) [list $self run]
       }
   }

   # stop
   # 
   # Stop running
   method stop {} {
       after cancel [list $self run]
   }
}

#-----------------------------------------------------------------------
# The Main GUI
#
# This GUI really just adds a toolbar to the basic board; in a sense,
# it's inheriting and extending the board.

snit::widget lifegame {
   # Delegate -cells and -pixels to the board, so that clients can
   # specify the board size; delegate other options to the hull.
   delegate option -cells to board
   delegate option -pixels to board
   delegate option * to hull

   # Frames don't have any methods but configure and cget, which are
   # already taken care of; so delegate everything else straight to the
   # board.
   delegate method * to board

   constructor {args} {
       frame $win.boardframe -borderwidth 5 -relief ridge
       set board [board $win.boardframe.board]
       pack $win.boardframe.board
       pack $win.boardframe -side bottom -padx 2 -pady 2

       bind . <Return> [mymethod generate]

       frame $win.bar

       $self addbtn "Generate" generate
       $self addbtn "Run"      run
       $self addbtn "Stop"     stop
       $self addbtn "Clear"    clear

       button $win.bar.exit -text "Exit" -command exit
       pack $win.bar.exit -side right -padx 2 -pady 2

       pack $win.bar -side top -fill x

       # Configure the options
       $self configurelist $args
   }


   # Private method: add a button to the toolbar
   method addbtn {text method} {
       button $win.bar.$method -text $text -command [mymethod $method]
       pack $win.bar.$method -side left -padx 2 -pady 2
   }
}

#-----------------------------------------------------------------------
# The Main program

lifegame .lifegame -cells 40 -pixels 15

pack .lifegame -side bottom -fill both -padx 2 -pady 2

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• artificial life

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