Multiple (virtual) dispatch is a central feature of C++ (and I suspect Java as well).
Print(Vehicle v){
print("vehicle");
}
Print(Car c){
print("car");
}
Print(Boat b){
print("boat");
}
Vehicle test = Boat();
Print(test);
class Vehicle {
virtual void Collide(Vehicle other);
}
class Car {
void Collide(Truck other) { /* hit a truck */ }
void Collide(Car other) { /* hit another car */ }
}
class Truck {
void Collide(Truck other) { /* hit another truck */ }
void Collide(Car other) { /* hit a car */ }
}
Vehicle c = Car();
Vehicle t = Truck();
c.Collide(t); // with multiple dispatch, calls Car::Collide(Truck)Multiple dispatch is typically meant to be purely dynamic in meaning, as wiki puts it:
> Multiple dispatch or multimethods is a feature of some programming languages in which a function or method can be dynamically dispatched based on the run-time (dynamic) type or, in the more general case some other attribute, of more than one of its arguments.[1]
Overloading and overriding are duals; the former is statically determined, the latter dynamically determined. Just like you can overload on the full argument list, multiple dispatch lets you override on the full argument list. This lets you do things like implement the visitor pattern without double dispatch. And C++ doesn't support it without libraries.
Can you give a small bit of sample code to demonstrate what you mean?