Question

We now have a framework to simulate these more lifelike creatures. We could put the critters from the old world into it, but they would just die since they don’t have an energy property. So let’s make new ones. First we’ll write a plant, which is a rather simple life-form.

function Plant() {
  this.energy = 3 + Math.random() * 4;
}
Plant.prototype.act = function(view) {
  if (this.energy > 15) {
    var space = view.find(" ");
    if (space)
      return {type: "reproduce", direction: space};
  }
  if (this.energy < 20)
    return {type: "grow"};
};

Plants start with an energy level between 3 and 7, randomized so that they don’t all reproduce in the same turn. When a plant reaches 15 energy points and there is empty space nearby, it reproduces into that empty space. If a plant can’t reproduce, it simply grows until it reaches energy level 20.

We now define a plant eater.

function PlantEater() {
  this.energy = 20;
}
PlantEater.prototype.act = function(view) {
  var space = view.find(" ");
  if (this.energy > 60 && space)
    return {type: "reproduce", direction: space};
  var plant = view.find("*");
  if (plant)
    return {type: "eat", direction: plant};
  if (space)
    return {type: "move", direction: space};
};

We’ll use the * character for plants, so that’s what this creature will look for when it searches for food.

This is a book about getting computers to do what you want them to do. Computers are about as common as screwdrivers today, but they contain a lot more hidden complexity and thus are harder to operate and understand. To many, they remain alien, slightly threatening things.