Inheritance

As for multiple programming language, inheritance can be used in GAML. It is used to structure better your code, when you have some complex models.

Index

• Mother species / child species
• Virtual actions
• Get all the subspecies from a species

Mother species / child species

To make a species inherit from a mother species, you have to add the facet parent, and specify the mother species.

species mother_species {
}

species child_species parent:mother_species {
}

Thus, all the attributes, actions and reflex of the mother species are inherited to the child species.

species mother_species {
	int attribute_A;
	action action_A {}
}

species child_species parent:mother_species {
	init {
		attribute_A <- 5;
		do action_A;
	}
}

If the mother species has a particular skill, its children will inherit all the attributes and actions.

species mother_species skills:[moving] {
}

species child_species parent:mother_species {
	init {
		speed <- 2.0;
	}
	reflex update {
		do wander;
	}
}

You can redefine an action or a reflex by declaring an action or a reflex with the same name.

Virtual action

You have also the possibility to declare a virtual action in the mother species, which means an action without implementation, by using the facet virtual:

action virtual_action virtual:true;

When you declare an action as virtual in a species, this species becomes abstract, which means you cannot instantiate agent from it. All the children of this species has to implement this virtual action.

species virtual_mother_species {
	action my_action virtual:true;
}

species child_species parent:virtual_mother_species {
	action my_action {
		// some statements
	}
}

Get all the subspecies from a species

If you declare a “mother” species, you create a “child” agent, then “mother” will return the population of agents “mother” and not the population of agents “child”, as it is shown in the following example :

global
{
    init {
        create child number:2;
        create mother number:1;
    }
    reflex update {
        write length(mother); // will write 1 and not 3
    }
}

species mother {}

species child parent:mother {}

We reminds you that “subspecies” is a built-in attribute of the agent. Using this attribute, you can easily get all the subspecies agents of the mother species by writing the following gaml function :

global
{
    init {
        create child number:2;
        create mother number:1;
    }
    reflex update {
        write length(get_all_instances(mother)); // will write 3 (1+2)
    }
    list<agent> get_all_instances(species<agent> spec) {
        return spec.population +  spec.subspecies accumulate (get_all_instances(each));
    }
}

species mother {}

species child parent:mother {}