Ant Colony

breed [food-source
       food-sources]
breed [ants]
ants-own [original_x_location 
          original_y_location]
patches-own [
  chemical             ;; amount of chemical on this patch
  ground               ;; color of ground                 ;; amount of food on this patch (1 or 2)
  food                ;; true on nest patches, false elsewhere
  nest-scent]           ;; number that is higher closer to the nest

;;;;;;;;;;;;;;;;;;;;;;;;
;;; Setup procedures ;;;
;;;;;;;;;;;;;;;;;;;;;;;;

to setup
  ;; (for this model to work with NetLogo's new plotting features,
  ;; __clear-all-and-reset-ticks should be replaced with clear-all at
  ;; the beginning of your setup procedure and reset-ticks at the end
  ;; of the procedure.)
  __clear-all-and-reset-ticks
  set-default-shape turtles "ant"  ;; makes them look like ants
  resize-world -40 40 -40 40
  ;;resize-world -30 30 -30 30
  setup-food-sources
end 

;;;;;;;;;;;;;;;;;;;;;
;;; Go procedures ;;;
;;;;;;;;;;;;;;;;;;;;;

to setup-food-sources
   set-default-shape food-source "circle"
  create-food-source number-of-food-sources [setxy random-xcor random-ycor] 
  ask food-source [set food number-of-food-sources]
  ask food-source [hatch-ants 1]
    ask ants[set size 3         ;; easier to see
    set color red 
    set original_x_location xcor
    set original_y_location ycor]    ;; red = not carrying food
end 

to go  ;; forever button
  ask ants
  [  look-for-food         ;; not carrying food? look for it
     return-to-nest        ;; carrying food? take it back to nest
    fd 1 ]
  diffuse chemical (diffusion-rate / 100)
  ask patches
  [ set chemical chemical * (100 - evaporation-rate) / 100  ;; slowly evaporate chemical
     ]
  ;add-ants
  tick
end 

to return-to-nest  ;; turtle procedure
  ask ants [setxy original_x_location original_y_location]
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; get from original code
   set chemical chemical + 60  ;; drop some chemical
    uphill-nest-scent        ;; head toward the greatest value of nest-scent
end 

to look-for-food  ;; turtle procedure
  wiggle
  if not can-move? 1 [ rt 180 ] 
  if xcor = original_x_location and ycor = original_y_location [fd 2] ;;;;;;;;;;;;;;;;;;;;;;;;;;;get ants to ignore food on original food-source
  if food > 0
  [         ;; pick up food
    set food food - 1        ;; and reduce the food source
    rt 180                   ;; and turn around
    stop ]
  ;; go in the direction where the chemical smell is strongest
  if (chemical >= Chem-Low-Threshold) and (chemical < Chem-Upper-Threshold)
  [ uphill-chemical ]
end 

;; sniff forward, left, and right, and go where the strongest smell is

to uphill-chemical  ;; turtle procedure
  let scent-ahead chemical-scent-at-angle   0
  let scent-right chemical-scent-at-angle  LoS
  let scent-left  chemical-scent-at-angle  (LoS * -1)
  if (scent-right > scent-ahead) or (scent-left > scent-ahead)
  [ ifelse scent-right > scent-left
    [ rt LoS ]
    [ lt LoS ] ]
end 

;; sniff left and right, and go where the strongest smell is

to uphill-nest-scent  ;; turtle procedure
  let scent-ahead nest-scent-at-angle   0
  let scent-right nest-scent-at-angle  LoS
  let scent-left  nest-scent-at-angle  (LoS * -1)
  if (scent-right > scent-ahead) or (scent-left > scent-ahead)
  [ ifelse scent-right > scent-left
    [ rt LoS ]
    [ lt LoS ] ]
end 

to wiggle  ;; turtle procedure
  rt random-normal 0 amount-of-wiggle
  ;; lt random-normal 0 amount-of-wiggle
  ;; if not can-move? 1 [ rt 180 ]
end 

to-report nest-scent-at-angle [angle]
  let p patch-right-and-ahead angle 1
  if p = nobody [ report 0 ]
  report [nest-scent] of p
end 

to-report chemical-scent-at-angle [angle]
  let p patch-right-and-ahead angle 1
  if p = nobody [ report 0 ]
  report [chemical] of p
end 

;; Credit to 1997 Uri Wilensky for frame of program