Ants/Gorskina

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patches-own [

 chemical             ;; amount of chemical on this patch
 food                 ;; amount of food on this patch (0, 1, or 2)
 nest?                ;; true on nest patches, false elsewhere
 nest-scent           ;; number that is higher closer to the nest
 food-source-number   ;; number (1, 2, or 3) to identify the food sources

]

Setup procedures ;;;

to setup

 clear-all
 set-default-shape turtles "bug"
 create-turtles population
 [ set size 2         ;; easier to see
   set color red  ]   ;; red = not carrying food
 setup-patches
 reset-ticks

end

to setup-patches

 ask patches
 [ setup-nest
   setup-food
   recolor-patch ]

end

to setup-nest  ;; patch procedure

 ;; set nest? variable to true inside the nest, false elsewhere
 set nest? (distancexy 0 0) < 5
 ;; spread a nest-scent over the whole world -- stronger near the nest
 set nest-scent 200 - distancexy 0 0

end

to setup-food  ;; patch procedure

 ;; setup food source one on the right
 if (distancexy (0.6 * max-pxcor) 0) < 5
 [ set food-source-number 1 ]
 ;; setup food source two on the lower-left
 if (distancexy (-0.6 * max-pxcor) (-0.6 * max-pycor)) < 5
 [ set food-source-number 2 ]
 ;; setup food source three on the upper-left
 if (distancexy (-0.8 * max-pxcor) (0.8 * max-pycor)) < 5
 [ set food-source-number 3 ]
 ;; set "food" at sources to either 1 or 2, randomly
 if food-source-number > 0
 [ set food one-of [1 2] ]

end

to recolor-patch  ;; patch procedure

 ;; give color to nest and food sources
 ifelse nest?
 [ set pcolor violet ]
 [ ifelse food > 0
   [ if food-source-number = 1 [ set pcolor cyan ]
     if food-source-number = 2 [ set pcolor sky  ]
     if food-source-number = 3 [ set pcolor blue ] ]
   ;; scale color to show chemical concentration
   [ set pcolor scale-color green chemical 0.1 5 ] ]

end

Go procedures ;;;

to go  ;; forever button

 ask turtles
 [ if who >= ticks [ stop ] ;; delay initial departure
   ifelse color = red
   [ look-for-food  ]       ;; not carrying food? look for it
   [ return-to-nest ]       ;; carrying food? take it back to nest
   wiggle
   fd 1 ]
 diffuse chemical (diffusion-rate / 100)
 ask patches
 [ set chemical chemical * (100 - evaporation-rate) / 100  ;; slowly evaporate chemical
   recolor-patch ]
 tick

end

to return-to-nest  ;; turtle procedure

 ifelse nest?
 [ ;; drop food and head out again
   set color red
   rt 180 ]
 [ 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

 if food > 0
 [ set color orange + 1     ;; 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 >= 0.05) and (chemical < 2)
 [ uphill-chemical ]

end

sniff 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  45
 let scent-left  chemical-scent-at-angle -45
 if (scent-right > scent-ahead) or (scent-left > scent-ahead)
 [ ifelse scent-right > scent-left
   [ rt 45 ]
   [ lt 45 ] ]

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  45
 let scent-left  nest-scent-at-angle -45
 if (scent-right > scent-ahead) or (scent-left > scent-ahead)
 [ ifelse scent-right > scent-left
   [ rt 45 ]
   [ lt 45 ] ]

end

to wiggle  ;; turtle procedure

 rt random 40
 lt random 40
 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 </syntaxhighlight>

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