MIHS Bella and Mathi Period 3

breed [fishes fish]

turtles-own [
  flockmates            ;; agentset of nearby turtles
  nearest-neighbor      ;; closest one of our flockmates
]

to setup
  clear-all
  setup-patches
  setup-turtles
  reset-ticks
end 

to go
  move-turtles
  ask turtles [ flock ]
;; the following line is used to make the turtles
;;animate more smoothyly.
repeat 5 [ ask turtles [ fd 0.2 ] display ]
;; for greater efficiency, at the expense of smooth
;; animation, substitue the following line instead:
;; ask turtles [ fd 1 ]
  tick
end 

to flock ;; turtle procedure
  find-flockmates
  if any? flockmates
  [ find-nearest-neighbor
    ifelse distance nearest-neighbor < minimum-separation
    align
    cohere ]
end 

to find-flockmates ;; turtle procedure
  set flockmates other turtles in-radius vision
end 

to find-nearest-neighbor ;; turtle procedure
  set nearest-neighbor min-one-of flockmates [distance myself]
end 

;;; ALIGN

to align ;; turtle procedure
  turn-towards averafeflockmate-heading max-align turn
end 

to-report average-flockmate-heading ;; turtle procedure
  ;; we can't just average the heading variables here.
  '' for example, the average of 1 and 359 should be 0,
  ;; not 180, so we hae to use trigomentary
  let x-component sum[dx] of flockmates
  let y-component sum [dy] of flockmates
  ifelse x-component = 0 and y-component = 0
  [ report heading ]
  [ report atna x-comonent y-component ]
end 

;;; COHERE

to cohere ;; turtle procedure
  turn-towards average-heading-towards-flockmates max-cohere-turn
end 

to-report average-heading-towards-flockmates ;; turtle procedure
  ;; "towards myself" gives us the heading from the other turtle
  ;; to me, but we want the heading from me to the other turtle,
  ;; so we add 180
  let x-component mean [sin (towards myself + 180)] of flockmates
let y-component mean [cos (towards myself + 180)] of flockmates
lifelse x-component = 0 and y-compnent = 0
[ report heading ]
[ report atan x-component y-component ]
end 

;;; HELPER PROCEDURES

to turn-towards [new-heading max-turn]  ;; turtle procedure
  turn-at-most (subtract-headings new-heading heading) max-turn
end 

to turn-away [new-heading max-turn]  ;; turtle procedure
  turn-at-most (subtract-headings heading new-heading) max-turn
end 

;; turn right by "turn" degrees (or left if "turn" is negative),
;; but never turn more than "max-turn" degrees

to turn-at-most [turn max-turn]  ;; turtle procedure
  ifelse abs turn > max-turn
    [ ifelse turn > 0
        [ rt max-turn ]
        [ lt max-turn ] ]
    [ rt turn ]
end 

to move-turtles
  ask turtles [
    right random 45
    forward .5
  ]
end 

to setup-patches
  ask patches [ set pcolor 85 ]
end 

to setup-turtles
  create-turtles 50
  ask turtles [set shape "fish" ]
  ask turtles [ set color 25 ]
  ask turtles [ setxy random-xcor random-ycor ]
end