turtles-own [message? other-turtle]

to setup
  ca
  cct 200 [
    set message? false
    fd random (4 * screen-edge-y)                 ; initialize turtle locations at random screen positions
  ]
  set message?-of random-one-of turtles true       ; give the message to one of the turtles
  ask turtles [
    color-turtles                                 ; color the turtles red if they have the message, blue otherwise
  ]
end

to go
  every 0.1 [
    ask turtles [move]
    ask turtles [                                    ;;when they're all done moving, start a new "ask turtles"
     communicate
     color-turtles  
    ]
  ]
end

; move randomly
to move  ;a turtle procedure
  fd random 4
  ; turn a random amount between -40 and 40 degrees,
  ; keeping the average turn at 0
  rt random 40
  lt random 40
end

; the core procedure!
to communicate ;;a turtle procedure
  set other-turtle random-one-of other-turtles-here  ; get the ID of another turtle on your patch
  if(other-turtle != nobody)                              ; if there is one there
    [if message?-of other-turtle                     ; (only IDs of 0 and above are valid)
      [set message? true]                            ; if the other turtle has the message
    ]                                                ; get the message
end

; color turtles with message red, and those without message blue
to color-turtles  ; a turtle procedure
  ifelse message?
    [set color red]
    [set color blue]
end


; This model was created as part of the project: CONNECTED MATHEMATICS:
; MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECT-BASED PARALLEL
; MODELS (OBPML)
; The project gratefully acknowledges the support of the National Science
; Foundation (Applications of Advanced Technologies Program) -- grant numbers
; RED #9552950 and REC #9632612.
; 
; Copyright 1999  by Uri Wilensky. All rights reserved.
; Converted to NetLogo from StarLogoT, 2001.
;
; Permission to use, copy, or modify this software and its documentation for
; educational and research purposes only and without fee is hereby granted,
; provided that this copyright notice and the original authors' names appear
; on all copies and supporting documentation. For any other uses of this
; software, in original or modified form, including but not limited to
; distribution in whole or in part, specific prior permission must be
; obtained from Uri Wilensky. These programs shall not be used, rewritten, or
; adapted as the basis of a commercial software or hardware product without
; first obtaining appropriate licenses from Uri Wilensky. We make no
; representations about the suitability of this software for any purpose. It
; is provided "as is" without express or implied warranty.
@#$#@#$#@
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Command Center

BUTTON
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setup
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OBSERVER

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BUTTON
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setup
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MONITOR
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count turtles with [color = red]
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1

GRAPHICS-WINDOW
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@#$#@#$#@
WHAT IS IT?
-----------
This code example is a simple demo of turtle-turtle communications. One turtle starts out with a message (the red turtle) and she spreads the message to other turtles.

The monitor keeps track of how many turtles have the message by reporting:
  count turtles with [color = red]

Note that if you put a procedure inside an "ask turtles [  ]" bracket, then everything in that procedure will be executed by all of the turtles.
@#$#@#$#@
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NetLogo 1.0 Beta 8d
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