;;  This procedure sets up the patches and turtles
breed [farmers farmer]
breed [pigs pig]
globals[pig-over?
        scared

        ]
farmers-own [ new-heading ]
to setup

  ;;  Clear everything.
  clear-all

  set scared 1
  set pig-over? false

  ;;  Set Environment
  set-default-shape farmers "person farmer"
  set-default-shape pigs "pig"

  ask patches with [pxcor mod 2 = 1 and
                    pycor mod 2 = 1]
    [ set pcolor 5 ]


  ask patches with [count neighbors != 8]
    [ set pcolor 5 ]

  ;;  This will create turtles

  create-farmers Num_Farmer
  [
    set size 1
    set color one-of remove blue base-colors
    let empty patches with [pcolor != 5]  with [not any? turtles-here]
    move-to one-of empty

  ]

  create-pigs Num_Pigs
  [
    set size 1
    set color 127
    let empty patches with [pcolor != 5]  with [not any? turtles-here]
    move-to one-of empty
    ;set color one-of remove gray base-colors
  ]

  reset-ticks
end


to go
  ;;condition for stop
  if not any? pigs
    [ set pig-over? true ]
  if pig-over?
    [ user-message word "Porcos capturados! Total de ticks: " ticks
      stop]
  ;;movement functions
  ask farmers[
   move-farmer
  ]
  ask pigs [
    move-pig
  ]
  ;; make the farmer capture the pig
  ask farmers[
    catch-pig
  ]
tick
end


to catch-pig
  ;; verific if have a pig near the farmer and select one to die
  let nearpatch neighbors4
  let nearpigs pigs-on nearpatch
  if one-of nearpigs != nobody
  [
    ask one-of nearpigs[
    die
    ]
  ]

end

to move-farmer
  ;; movement function where the farmer will analyze which pig is closest and will follow him

  let dist_up 99
  let dist_down 99
  let dist_right 99
  let dist_left 99

  let closest min-one-of pigs [distance myself]

  if [pcolor] of patch-at 0 1 != 5
    [
      let u_farm patch-at 0 1
      ask closest[ set dist_up distance u_farm
       ]
    ]
  if [pcolor] of patch-at 1 0 != 5
    [
      let r_farm patch-at 1 0
      ask closest[ set dist_right distance r_farm
       ]
    ]
  if [pcolor] of patch-at 0 -1 != 5
    [
      let d_farm patch-at 0 -1
      ask closest[ set dist_down distance d_farm
       ]
    ]
  if [pcolor] of patch-at -1 0 != 5
    [
      let l_farm patch-at -1 0
      ask closest[ set dist_left distance l_farm
       ]
    ]

  let mindist min (list dist_up dist_down dist_left dist_right)
  if mindist = dist_up [
    move-up ]
  if mindist = dist_down [
    move-down ]
  if mindist = dist_left [
    move-left ]
  if mindist = dist_right [
    move-right ]
  if not any? turtles-on patch-ahead 1
    [ fd 1 ]
end

to move-pig
  ;; pig move function, works similar to move-farmer but in an inverted way

  let dist_up -99
  let dist_down -99
  let dist_right -99
  let dist_left -99

  let closest min-one-of farmers [distance myself]


  if [pcolor] of patch-at 0 1 != 5
    [
      let u_pig patch-at 0 1
      ask closest[ set dist_up distance u_pig
       ]
    ]
  if [pcolor] of patch-at 1 0 != 5
    [
      let r_pig patch-at 1 0
      ask closest[ set dist_right distance r_pig
       ]
    ]
  if [pcolor] of patch-at 0 -1 != 5
    [
      let d_pig patch-at 0 -1
      ask closest[ set dist_down distance d_pig
       ]
    ]
  if [pcolor] of patch-at -1 0 != 5
    [
      let l_pig patch-at -1 0
      ask closest[ set dist_left distance l_pig
       ]
    ]

  let maxdist max (list dist_up dist_down dist_left dist_right)
  if maxdist = dist_up [
    move-up ]
  if maxdist = dist_down [
    move-down ]
  if maxdist = dist_left [
    move-left ]
  if maxdist = dist_right [
    move-right ]

  if not any? turtles-on patch-ahead 1
    [ fd 1 ]

end

to move-left
  set heading 270
end

to move-right
  set heading 90
end

to move-up
  set heading 0
end

to move-down
  set heading 180
end
@#$#@#$#@
GRAPHICS-WINDOW
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554
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BUTTON
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PLOT
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"" ""
PENS
"Pigs" 1.0 0 -5825686 true "" "plot count pigs"

MONITOR
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Pigs
count pigs
3
1
11

@#$#@#$#@
## WHAT IS IT?

This code example shows how to have turtles look ahead before they move.  By looking ahead, a turtle can determine what is in front of it and take a particular action.  Looking ahead is most appropriate in situations where the turtle is not supposed to go "on top of" certain agents.  This can be extremely useful for something like barriers or walls, which the turtle shouldn't move through.

In this example, four turtles are placed in a world with a checkerboard-like pattern of blue barriers on which they are not allowed to step.  Before the turtles step forward they always check ahead to see if they are about to move into a wall using the patch-ahead primitives.  `patch-ahead n` reports the patch that the turtle would be on if it were to move forward `n` steps (e.g., by executing `fd n`). In this example, we want turtles to always move one step at a time, so we always use `patch-ahead 1`.

In addition to simulating barriers, this technique can also be used to test whether a turtle is near something important, such as food or another turtle.

Note that the code in this model only prevents the turtle from landing on a blue patch. It doesn't prevent the turtle from:

- following a path which crosses a blue patch
- visually touching a blue patch

The turtles may cross a blue patch because in NetLogo the `fd 1` command is equivalent to `jump 1` -- in other words, the turtle simply disappears from its old location and reappears in its new location, rather than moving continuously.  You could add more code to the model to ensure that the turtle's path never crossed a blue patch, but the math for that gets a bit complicated.

The turtles may visually touch a blue patch because to NetLogo, the turtles are really just their center points.  We represent the turtle visually with a certain size and shape, but to NetLogo, the turtle is a point with no extent, and that point is always on one and only one patch.  Again, you could add "collision detection" code to the model to ensure that the center point never came within a certain distance of any patch, but the math for that would get complicated.  This kind of "collision detection" is not built in to NetLogo.

## RELATED MODELS

* Next Patch Example
* One Turtle Per Patch Example

To see this in use in real models see Ants, Slime, Gas Chromatography, Simple Kinetics, GasLab and Connected Chemistry models, various games, and Wealth Distribution.

<!-- 2004 -->
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NetLogo 6.1.1
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