More dimensions

In this section, we see that it is possible to define a multimethod with more than two dimensions. We define a multimethod with four dimensions:

Method4<String> foo4 = new Method4<String>().add(new Cases() {
				
	String match(I x, I y, I z, I t) {
		return "default";
	}
	
	String match(A x, A y, A z, A t) {
		return "A, A, A, A = " + x.id + ", " + y.id + ", " + z.id + ", " + t.id;
	}
	
	String match(A x, B y, C z, D t) {
		return "A, B, C, D = " + x.id + ", " + y.fd + ", " + z.fd + ", " + t.id;
	}
});

Note that this time we defined some kind of a default match() method for the hierarchy of types containing the root interface I and the classes A, B, C and D. With such a definition we ensure that for any combination of types in that hierarchy, there will be a matching match() method.

To test it, we define in a print() method:

public static void print(Method4<String> foo4, I obj1, I obj2, I obj3, I obj4) throws Throwable {
		
	String res = foo4.invoke(obj1, obj2, obj3, obj4);
	System.out.println(obj1.getClass().getName() + ", "
				+ obj2.getClass().getName() + ", " 
				+ obj3.getClass().getName() + ", " 
				+ obj4.getClass().getName() + " -> " + res);
}

And we call it with some tuples:

print(foo4, a, a, a, a); // A, A, A, A... 
print(foo4, d, a, c, b); // default
print(foo4, a, b, c, d); // A, B, C, D...

The tuples with dynamic types (A, A, A, A) and (A, B, C, D) have a perfect match however (D, A, C, B) has not and the default match() method is called.

Note that EVL multimethods are currently limited to seven dimensions but it is just because it was necessary to set a limit. However it is very easy to extend to any number of dimensions.