Courses/CS 461/Winter 2006/Jesse Zwerling/Homework 1

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grass_rabbits_wolves

 breeds [rabbits wolves]
 turtles-own [ energy ]
 rabbits-own [ grabbed?]
 to setup
   ca
     ct
   cp
   clear-plot
   ask patches [ set pcolor green ]
   grow-grass
   set-default-shape rabbits "rabbit"
   create-custom-rabbits number-rabbits [
     set color white
     randomize-position
     set energy random 10  ;start with a random amt. of energy
     set grabbed? false
   ]
   set-default-shape wolves "wolf"
   create-custom-wolves initial-number-wolves  ;; create the wolves, then initialize their variables
   [
     set color black
     set energy random (2 * wolf-gain-from-food)
     setxy random-float screen-size-x
           random-float screen-size-y
     set size 1.5
   ]
   setup-plot
   do-plot
 end
 to go
   grow-grass
   move
   do-plot
   if not any? turtles
     [ stop ]
 end  
 to move
   ask rabbits
   [ step
     eat-grass
     reproduce
     death ]
    ask wolves [
     step
     catch-rabbits
     reproduce-wolves
     death
   ]
 end  
 to catch-rabbits  ;; wolf procedure
   let prey random-one-of (rabbits-here             ;; grab a random sheep
                            with [not grabbed?]) ;; that no one else is grabbing
   if prey != nobody                             ;; did we get one?  if so,
     [ set grabbed?-of prey true                 ;; prevent other wolves from grabbing it
       ask prey [ die ]                          ;; kill it
       set energy energy + wolf-gain-from-food ]     ;; get energy from eating
 end 
 to reproduce-wolves  ;; wolf procedure
   if random-float 100 < wolf-reproduction-rate [  ;; throw "dice" to see if you will reproduce
     set energy (energy / 2 )  ;; divide energy between parent and offspring
     hatch 1 [ rt random-float 360 fd 1 ]  ;; hatch an offspring and move it forward 1 step
   ]
 end
 to grow-grass
    ask patches [
     if pcolor = brown [
       if ( random-float 1000 ) < grass-grow-rate
         [ set pcolor green ]
   ] ]
 end 
 to step   ;moving takes some energy
   rt random-float 50
   lt random-float 50
   fd 1
   set energy ( energy - 0.5 )
 end 
 to eat-grass       ;;gain "grass-energy" by eating grass
   if ( pcolor = green )
   [ set pcolor brown
     set energy ( energy + grass-energy ) ]
 end 
 to reproduce     ;;give birth to a new rabbit, but it takes lots of energy
   if ( energy > rabbit-reproduction )
     [ set energy ( energy / 2 )
       hatch 1 [ fd 1 ] ]
 end
 to death     ;;die if you run out of energy
   if ( energy < 0 )
     [ die ]
 end
 to do-plot
   set-current-plot "Populations"
   set-current-plot-pen "grass"
   plot ( ( count patches with [pcolor = green] ) / 4 )
   set-current-plot-pen "rabbits"
   plot count turtles
   set-current-plot-pen "weeds"
   plot ( ( count patches with [pcolor = violet] ) / 4 )
   set-current-plot-pen "wolves"
   plot ( ( count turtles with [pcolor = black] ) / 4 )
 end
 to randomize-position
   setxy random-float screen-size-x
         random-float screen-size-y
 end
 to setup-plot ;; set up plotting
   set-current-plot "Populations"
   set-plot-y-range 0 number-rabbits
 end