Lamprey and Trout modeling

globals [ max-trouts ]  ; don't let trouts population grow too large
; trouts and lampreys are both breeds of turtle.
breed [ trouts a-trouts ]  ; trouts is its own plural, so we use "a-trouts" as the singular.
breed [ lampreys a-lampreys ]
turtles-own [ energy ]       ; both lampreys and trouts have energy
patches-own [ countdown ]

to setup
  clear-all
  ifelse netlogo-web? [set max-trouts 10000] [set max-trouts 30000]

  ; Check model-version switch
  ; if we're not modeling plankton, then the trouts don't need to eat to survive
  ; otherwise the plankton's state of growth and growing logic need to be set up
  ifelse model-version = "trouts-lampreys-plankton" [
    ask patches [
      set pcolor one-of [ green brown ]
      ifelse pcolor = green
        [ set countdown plankton-regrowth-time ]
      [ set countdown random plankton-regrowth-time ] ; initialize plankton regrowth clocks randomly for brown patches
    ]
  ]
  [
    ask patches [ set pcolor green ]
  ]

  create-trouts initial-number-trouts  ; create the trouts, then initialize their variables
  [
    set shape  "fish"
    set color white
    set size 1.5  ; easier to see
    set label-color blue - 2
    set energy random (2 * trouts-gain-from-food)
    setxy random-xcor random-ycor
  ]

  create-lampreys initial-number-lampreys  ; create the lampreys, then initialize their variables
  [
    set shape "line"
    set color black
    set size 2  ; easier to see
    set energy random (2 * lampreys-gain-from-food)
    setxy random-xcor random-ycor
  ]
  display-labels
  reset-ticks
end 

to go
  ; stop the simulation of no lampreys or trouts
  if not any? turtles [ stop ]
  ; stop the model if there are no lampreys and the number of trouts gets very large
  if not any? lampreys and count trouts > max-trouts [ user-message "The trouts have inherited the earth" stop ]
  ask trouts [
    move
    if model-version = "trouts-lampreys-plankton" [ ; in this version, trouts eat plankton, plankton grows and it costs trouts energy to move
      set energy energy - 1  ; deduct energy for trouts only if running trouts-lampreys-plankton model version
      eat-plankton  ; trouts eat plankton only if running trouts-lampreys-plankton model version
      death ; trouts die from starvation only if running trouts-lampreys-plankton model version
    ]
    reproduce-trouts  ; trouts reproduce at random rate governed by slider
  ]
  ask lampreys [
    move
    set energy energy - 1  ; lampreys lose energy as they move
    eat-trouts ; lampreys eat a trouts on their patch
    death ; lampreys die if our of energy
    reproduce-lampreys ; lampreys reproduce at random rate governed by slider
  ]
  if model-version = "trouts-lampreys-plankton" [ ask patches [ grow-plankton ] ]
  ; set plankton count patches with [pcolor = green]
  tick
  display-labels
end 

to move  ; turtle procedure
  rt random 50
  lt random 50
  fd 1
end 

to eat-plankton  ; trouts procedure
  ; trouts eat plankton, turn the patch brown
  if pcolor = green [
    set pcolor brown
    set energy energy + trouts-gain-from-food  ; trouts gain energy by eating
  ]
end 

to reproduce-trouts  ; trouts procedure
  if random-float 100 < trouts-reproduce [  ; throw "dice" to see if you will reproduce
    set energy (energy / 2)                ; divide energy between parent and offspring
    hatch 1 [ rt random-float 360 fd 1 ]   ; hatch an offspring and move it forward 1 step
  ]
end 

to reproduce-lampreys  ; lampreys procedure
  if random-float 100 < lampreys-reproduce [  ; throw "dice" to see if you will reproduce
    set energy (energy / 2)               ; divide energy between parent and offspring
    hatch 1 [ rt random-float 360 fd 1 ]  ; hatch an offspring and move it forward 1 step
  ]
end 

to eat-trouts  ; lampreys procedure
  let prey one-of trouts-here                    ; grab a random trouts
  if prey != nobody  [                          ; did we get one?  if so,
    ask prey [ die ]                            ; kill it, and...
    set energy energy + lampreys-gain-from-food     ; get energy from eating
  ]
end 

to death  ; turtle procedure (i.e. both lampreys nd trouts procedure)
  ; when energy dips below zero, die
  if energy < 0 [ die ]
end 

to grow-plankton  ; patch procedure
  ; countdown on brown patches: if reach 0, grow some plankton
  if pcolor = brown [
    ifelse countdown <= 0
      [ set pcolor green
        set countdown plankton-regrowth-time ]
      [ set countdown countdown - 1 ]
  ]
end 

to-report plankton
  ifelse model-version = "trouts-lampreys-plankton" [
    report patches with [pcolor = green]
  ]
  [ report 0 ]
end 

to display-labels
  ask turtles [ set label "" ]
  if show-energy? [
    ask lampreys [ set label round energy ]
    if model-version = "trouts-lampreys-plankton" [ ask trouts [ set label round energy ] ]
  ]
end 


; Copyright 1997 Uri Wilensky.
; See Info tab for full copyright and license.