Make turtles stop after crossing 5 patches in Netlogo?

Question

There are a certain number of turtles distributed on the lower part of the grid. Some of the turtles are “parents”, they hatch 1 offspring with each go procedure. Additionally, the turtles move around with each go procedure. Is there any way that I can make the turtles stop after crossing 5 patches and then change color, thus it is easy to see which turtles stopped moving?

breed [birds bird];my turtles

birds-own [
  parents?
]


to setup
  ca
  ask patches [set pcolor green]
  create-birds 100 [
    set color blue
    set size 2
    move-to one-of patches with [pycor < 50 ] ;100 x 100, wrapped,origin in the left bottom corner 
    set heading random 360
    set parents? false
  ]
  ask n-of 25 birds [set parents? true]
  reset-ticks
end

to go
 give-birth
 fly-around
 stop-flying 
  
  tick
end


  
to give-birth
  ask birds with [parents? = true][
    hatch 1 
  ]
end

to fly-around
  ask birds [
    fd 2 display
  ]
end

to stop-flying
  ask birds-on patches with [pycor > 70][  
;instead of pycor as a condition, I want them do stop and change color after crossing 5 patches.
    set color red
    stop
  ]
end
  

Maybe it can be done via ticks, but since there are new turtles hatching with each tick, the turtles do not all have the same number of ticks (some are younger than others).

Answer 1

Sure, the idea would be to let each bird use a counter to check how many times it changed patch. Everytime a bird moves, it will check if the patch it is on is different from the previous one; if that's true, the counter will be incremented by 1; when the counter reaches 5, the bird stops.

Given that your birds move by a distance greater than 1 (currently by 2, in your code), in order to use the counter as above I suggest to make them move one step at a time and check the patch after every step. You can do this by using repeat 2 [fd 1 ...] instead of using fd 2.

You can implement this as follows:

birds-own [
  counter
  last-patch
  stopped?
]

to setup
  ...
  create-birds 100 [
    ...
    set last-patch [patch-here]
    set stopped? FALSE
    ...
  ]
  ...
end

to fly-around
  repeat 2 [
    if (not stopped?) [
      fd 1
      if (patch-here != last-patch) [
        set counter counter + 1
        if (counter = 5) [
          set stopped? TRUE
          set color red
        ]
      ]
    ]
  ]
end

There is some room to make this code more efficient (for example: as of now each bird will check twice if (not stopped?), given that that's inside the repeat 2 [ ... ] command block, even if it already has stopped? = TRUE), but that's pretty much the logic.

A note:

• set heading random 360 is redundant in setup, as that's the default behaviour when turtles are created through create-turtles. However you might want to use it in hatch, as hatched turtles will inherit the parent's heading. That depends on your intentions.