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ThomasC
ThomasC

Reputation: 881

Why does netlogo count turtles on neighbours differently?

When I run the following two lines I get different answers. Does anybody know why? The first gives the answer I want:

ask turtles[
    let tempcol [color] of self
    show count (turtles-on neighbors4) with [color = tempcol]]

ask turtles[
    set nextcolor [color] of self
    let tempcol [color] of self
    show count (turtles-on neighbors4) with [color = [color] of self]]

Upvotes: 0

Views: 68

Answers (1)

Luke C
Luke C

Reputation: 10301

You're right in that the issue is with the use of self- from the dictionary entry for that primitive:

"self" is simple; it means "me". "myself" means "the agent who asked me to do what I'm doing right now.

In short, you want myselfin the second example. Currently, your second example is saying something like, "turtles, show the count of neighbor turtles whose color is the color of themselves" where you really want to say "turtles, show the count of neighbor turtles whose color is the color of myself." For a potentially clearer example, check out this setup:

to setup
  ca
  crt 10 [
    set color red
    setxy random-xcor random-ycor
  ] 
  ask n-of 3 turtles [
    set color blue
  ]
 reset-ticks 
end

This creates 7 red turtles and 3 blue turtles. Now, if you ask one of the blue turtles to show the count of of turtles with the same color as itself, we should expect it to return a value of 3. If you run that code using self, however, the value returned is 10- because all turtles have a color that is equal to the color of themselves:

to self-compare

  ask one-of turtles with [ color = blue ] [
    print "'[color] of self' example:"
    show count turtles with [ color = [color] of self ]
  ]

end

If you run the exact same code but use myself, it returns the answer we would expect:

to myself-compare

  ask one-of turtles with [ color = blue ] [
    print "'[color] of myself' example:"
    show count turtles with [ color = [color] of myself ]
  ] 

end

I would also point out that almost all of your of self statements are redundant-you should be able to take them all out (except for [color = [color] of self]] that you will be changing to a myself statement anyway) and have your code run as before.

Upvotes: 2

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