import std.stdio;
import std.traits;

class Greeter(T) {
    static if (__traits(hasMember, T, "name")) {
        T person;

        this(T person) {
            this.person = person;
        }

        void greet() {
            writefln("hello %s!", person.name);
        }
    }

    void genericGreet() {
        writeln("hello world!");
    }
}

class Person {
    string name;

    this(string name) {
        this.name = name;
    }
}

void main() {
    auto g1 = new Greeter!(int)();
    auto g2 = new Greeter!(Person)(new Person("Alex"));
    g1.genericGreet();
    g2.greet();
}