Little features: Add empty_struct, object_slicing

topic/little_features/empty_struct.cpp

@@ -0,0 +1,10 @@
+#include <iostream>
+
+// Emptry structs are valid in C++, not so in C.
+struct Empty {
+};
+
+int main()
+{
+	std::cout << sizeof(Empty) << "\n";
+}

topic/little_features/object_slicing.cpp

@@ -0,0 +1,54 @@
+#include <iostream>
+#include <memory>
+
+struct Shape {
+	virtual float area() const
+	{
+		std::cout << "Shape::area\n";
+		return 0;
+	}
+
+	virtual ~Shape() {}
+};
+
+struct Rect : public Shape {
+	Rect(float width, float height) : width(width), height(height) {}
+
+	float area() const override
+	{
+		std::cout << "Rect::area\n";
+		return width * height;
+	}
+
+	float width, height;
+};
+
+int main()
+{
+	std::cout << "size of Shape: " << sizeof(Shape) << "\n"
+	          << "size of Rect: " << sizeof(Rect) << "\n";
+
+	Rect rect{2.0f, 3.0f};
+	{
+		const auto area = rect.area();
+		std::cout << "Area of rect: " << area << "\n";
+	}
+
+	Shape shape = rect; // rect gets sliced to fit into shape.
+	{
+		const auto area = shape.area();
+		std::cout << "Area of shape: " << area << "\n";
+	}
+
+	Shape *shape_ptr = &rect;
+	{
+		const auto area = shape_ptr->area();
+		std::cout << "Area of shape_ptr: " << area << "\n";
+	}
+
+	std::shared_ptr<Shape> shape_sptr = std::make_shared<Rect>(3.0f, 4.0f);
+	{
+		const auto area = shape_sptr->area();
+		std::cout << "Area of shape_sptr: " << area << "\n";
+	}
+}