examples -> example

example/next.cpp

@@ -0,0 +1,74 @@
+// next.cpp
+// Copyright (c) 2018-2025 Jean-Louis Leroy
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+// Example taken Dylan's documentation, see
+// http://opendylan.org/documentation/intro-dylan/multiple-dispatch.html
+
+#include <iostream>
+
+#include <boost/openmethod.hpp>
+#include <boost/openmethod/compiler.hpp>
+
+using boost::openmethod::virtual_ptr;
+
+using namespace std;
+
+struct Vehicle {
+    virtual ~Vehicle() {
+    }
+};
+
+//[ car
+struct Car : Vehicle {};
+
+struct Truck : Vehicle {};
+
+struct Inspector {
+    virtual ~Inspector() {
+    }
+};
+
+struct StateInspector : Inspector {};
+
+BOOST_OPENMETHOD_CLASSES(Vehicle, Car, Truck, Inspector, StateInspector);
+
+BOOST_OPENMETHOD(
+    inspect, (virtual_ptr<const Vehicle>, virtual_ptr<const Inspector>), void);
+
+BOOST_OPENMETHOD_OVERRIDE(
+    inspect, (virtual_ptr<const Vehicle>, virtual_ptr<const Inspector>), void) {
+    cout << "Inspect vehicle.\n";
+}
+
+BOOST_OPENMETHOD_OVERRIDE(
+    inspect, (virtual_ptr<const Car> v, virtual_ptr<const Inspector> i), void) {
+    next(v, i);
+    cout << "Inspect seat belts.\n";
+}
+
+BOOST_OPENMETHOD_OVERRIDE(
+    inspect, (virtual_ptr<const Car> v, virtual_ptr<const StateInspector> i),
+    void) {
+    next(v, i);
+    cout << "Check road tax.\n";
+}
+
+auto main() -> int {
+    boost::openmethod::initialize();
+
+    const Vehicle& vehicle1 = Car();
+    const Inspector& inspector1 = StateInspector();
+    const Vehicle& vehicle2 = Truck();
+    const Inspector& inspector2 = Inspector();
+
+    cout << "First inspection:\n";
+    inspect(vehicle1, inspector1);
+
+    cout << "\nSecond inspection:\n";
+    inspect(vehicle2, inspector2);
+
+    return 0;
+}