State Machine Example

turtles-own [
  next-task  ;; task the turtle will run during this tick
  steps      ;; ...unless this number is greater than zero, in which
             ;; case this tick, the turtle just moves forward 1
]

to setup
  clear-all
  set-default-shape turtles "bug"
  ;; randomly distribute wood chips
  ask patches [
    if random-float 100 < density
      [ set pcolor yellow ]
  ]
  ;; randomly distribute termites
  crt number [
    set color white
    setxy random-xcor random-ycor
    set next-task task search-for-chip
    set size 5  ;; easier to see
  ]
  reset-ticks
end 

to go
  ask turtles
    [ ifelse steps > 0
        [ set steps steps - 1 ]
        [ run next-task
          wiggle ]
      fd 1 ]
  tick
end 

to wiggle  ;; turtle procedure
  rt random 50
  lt random 50
end 

to search-for-chip   ;; turtle procedure -- "picks up chip" by turning orange
  if pcolor = yellow
    [ set pcolor black
      set color orange
      set steps 20
      set next-task task find-new-pile ]
end 

to find-new-pile  ;; turtle procedure -- look for yellow patches
  if pcolor = yellow
    [ set next-task task put-down-chip ]
end 

to put-down-chip  ;; turtle procedure -- finds empty spot & drops chip
  if pcolor = black
   [ set pcolor yellow
     set color white
     set steps 20
     set next-task task get-away ]
end 

to get-away  ;; turtle procedure -- get out of yellow pile
  if pcolor = black
    [ set next-task task search-for-chip ]
end 


; Public Domain:
; To the extent possible under law, Uri Wilensky has waived all
; copyright and related or neighboring rights to this model.