Parental Investment Sexual Conflict

; Copyright 2018 César González.
; See Info tab for full copyright and license.

;# Breeds
turtles-own [
  ; state
  energy
  age
  nurturing

  ; g-type
  a-nurturing   ; sex-a nurturing time
  b-nurturing   ; sex-b nurturing time
  ;number-eggs  ; number of eggs spawn
  ;egg-size     ; energy provided to each descendent
]

breed [ sex-a a-organism ]
breed [ sex-b b-organism ]

patches-own [
  hatching
]

;# Constants

to-report adult-age report 80 end  ; age when an organism is mature and can reproduce

to-report stride    report 1  end  ; stride length

;# Main functions

to setup
  clear-all
  ; setup the terrain
  ask patches [
    set pcolor green + 1
    set hatching 0
  ]
  ; create the specimens, then initialize their variables
  set-default-shape sex-a "a-shape"
  set-default-shape sex-b "b-shape"
  create-turtles max-population
  ask turtles [
    ; initial state
    random-sex
    set age adult-age
    set size 3
    set energy random max-energy
    set nurturing 0
    setxy random-xcor random-ycor
    ; initial g-type
    set a-nurturing random hatch-age
    set b-nurturing random hatch-age
    ;set number-eggs random initial-number-eggs
    ;set egg-size random initial-egg-size
  ]
  reset-ticks
end 

to go
  ; stop simulation when any sex disappears
  if not any? sex-a or not any? sex-b [ stop ]
  ; control population
  if count turtles > max-population [
    ; above the maximum population the oldest die
    ask max-n-of (count turtles - max-population) turtles [age] [
      die
    ]
  ]
  ; organisms life
  ask turtles [
    be-born
    grow
    reproduce
    and-die
  ]
  ; gardening
  ask patches [
    clean-empty-eggs
  ]
  tick
end 

;# Procedures

to be-born ;.turtle
  ; Darwin says someone has done this for you
end 

to grow ;.turtle
  ; metabolism processes
  metabolise
  ; nurture offspring if any
  nurture
  ; wander around
  move
end 

to metabolise ;.turtle
  ; increase age
  set age age + 1
  ; eat
  set energy energy + 1
  ; change appearance with age
  if age = hatch-age [ set size 1 ]
  if age = adult-age [ set size 3 ]
end 

to nurture ;.turtle
  ; check the adult is nurturing
  if nurturing = 0 [ stop ]
  ; spend energy feeding offspring
  let offspring turtle-set turtles-here with [ size = 0 ]
  set energy energy - (count offspring * nurturing-energy)
  ask offspring [
    set energy energy + nurturing-energy
  ]
  set nurturing nurturing - 1
end 

to move ;.turtle
  ; check mobility
  if age < hatch-age or  ; eggs can't move
     nurturing > 0        ; when nurturing, stay at home
    [ stop ]
  ; take a step in a random direction
  right random-float 50
  left random-float 50
  forward stride
end 

to reproduce ;.turtle
  ; check mating conditions
  if breed = sex-b or    ; avoid duplicated couples
     age < adult-age or  ; adults only
     energy < min-energy-reproduce or  ; a minimum energy is required
     pcolor = white      ; only one egg cluster allowed at a patch
    [ stop ]
  ; find a suitable partner
  let parent-a self
  let parent-b one-of sex-b-here with [ age > adult-age and energy >= min-energy-reproduce ]
  let parents (turtle-set parent-a parent-b)
  if count parents = 2 [
    ; make a nest for the egg cluster
    ask patch-here [
      set pcolor white
      set hatching hatch-age
    ]
    ; spawn eggs and fecundate them
    set energy (energy - number-eggs * egg-size)
    hatch number-eggs [
      ; set initial offspring state
      set energy egg-size
      set age 0
      set size 0
      random-sex
      set nurturing 0
      ; inherit mutated g-type
      set a-nurturing mutate ([ a-nurturing ] of one-of parents)
      set b-nurturing mutate ([ b-nurturing ] of one-of parents)
      ;set number-eggs mutate ([ number-eggs ] of one-of parents) drift
      ;set egg-size mutate ([ egg-size ] of one-of parents) drift
    ]
    ; start nurturing
    ask parent-a [ set nurturing a-nurturing ]
    ask parent-b [ set nurturing b-nurturing ]
  ]
end 

to random-sex ;.turtle
  ifelse random 2 = 0 [
    set breed sex-a
    set color gray
  ] [
    set breed sex-b
    set color orange
  ]
end 

to and-die ;.turtle
  ; when energy reaches zero it's game over
  if energy <= 0 [ die ]
end 

to invasion [ n $a-nurturing $b-nurturing ]
  ; check parameter integrity
  if n < 0 or
     $a-nurturing < 0 or
     $b-nurturing < 0
    [ stop ]
  ; create an invasion of n organisms with given g-type
  create-turtles n [
    set a-nurturing $a-nurturing
    set b-nurturing $b-nurturing
    random-sex
    set color red
    set age adult-age
    set size 3
    set energy random max-energy
    set nurturing 0
    setxy random-xcor random-ycor
  ]
end 

to clean-empty-eggs ;.patch
  if hatching > 0 [ set hatching hatching - 1 ]
  if pcolor = white and hatching = 0 [
    set pcolor green + 1
  ]
end 

;# Reporters

to-report mutate [ gene ] ;.turtle
  let gene' gene + random-float drift - random-float drift
  if gene < 0 [ report 0 ] ; negative values make no sense
  report gene'
end