microworlds/core/turtle.go

package core

import (
	"math/rand"
)

type Turtle struct {
	xpos, ypos int
	heading    int
	actor      Actor
}

type NilActor struct {
}

func (NilActor) Setup(*Environment, *Turtle) {
}

func (NilActor) Run(*Environment, *Turtle) {
}

func NewTurtle(env *Environment, actor Actor) *Turtle {
	for {
		turtle := new(Turtle)
		turtle.xpos = rand.Intn(env.width)
		turtle.ypos = rand.Intn(env.height)
		turtle.actor = actor
		if env.Check(turtle.xpos, turtle.ypos) == false {
			actor.Setup(env, turtle)
			env.Occupy(turtle.xpos, turtle.ypos)
			turtle.setRandomHeading()
			return turtle
		}
	}

}

func (t *Turtle) Pos() (int, int) {
	return t.xpos, t.ypos
}

var headings = [][]int{{-1, -1}, {0, -1}, {1, -1}, {1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}}

func (t *Turtle) setRandomHeading() {
	t.heading = rand.Intn(8)
}

func (t *Turtle) SetXY(x, y int) {
	t.xpos = x
	t.ypos = y
}

func (t *Turtle) Wiggle() {
	wiggle := rand.Intn(3) - 1
	h := (t.heading + wiggle) % 8
	if h < 0 {
		h = 7
	}
	t.heading = h
}

func (t *Turtle) TurnAround() {
	t.heading = (t.heading + 4) % 8
}

func (t *Turtle) Drop(env *Environment, amount float32, pheromone string) {
	env.Mark(pheromone, t.xpos, t.ypos, amount)
}

func (t *Turtle) FollowGradient(env *Environment, distance int, threshold float32, pheromone string) {

	h0 := t.heading - 1
	if h0 < 0 {
		h0 = 7
	}

	dx0 := headings[h0][0] * distance
	dy0 := headings[h0][1] * distance

	x0 := (t.xpos + dx0)
	y0 := (t.ypos + dy0)

	dx := headings[t.heading][0] * distance
	dy := headings[t.heading][1] * distance

	x := (t.xpos + dx)
	y := (t.ypos + dy)

	h1 := (t.heading + 1) % 8
	dx1 := headings[h1][0] * distance
	dy1 := headings[h1][1] * distance

	x1 := (t.xpos + dx1)
	y1 := (t.ypos + dy1)

	as0 := env.SniffNormalized(x0, y0, pheromone)
	if as0 < threshold {
		as0 = 0
	}
	as := env.SniffNormalized(x, y, pheromone)
	if as < threshold {
		as = 0
	}
	as1 := env.SniffNormalized(x1, y1, pheromone)
	if as1 < threshold {
		as1 = 0
	}

	if as0 > as && as0 > as1 {
		t.heading = h0
	} else if as1 > as && as1 > as0 {
		t.heading = h1
	}
}

func (t *Turtle) Step(env *Environment) bool {
	dx := headings[t.heading][0]
	dy := headings[t.heading][1]

	ox := t.xpos
	oy := t.ypos
	env.Leave(ox, oy)
	t.xpos = (t.xpos + dx) % (env.width)
	if t.xpos < 0 {
		t.xpos = env.width - 1
	}
	t.ypos = (t.ypos + dy) % (env.height)
	if t.ypos < 0 {
		t.ypos = env.height - 1
	}

	success := true
	if env.Check(t.xpos, t.ypos) == true {
		t.xpos = ox
		t.ypos = oy
		success = false
	}
	env.Occupy(t.xpos, t.ypos)
	return success
}

// Run the turtle program
func (t *Turtle) Run(env *Environment) {
	t.actor.Run(env, t)
}