#include <iostream>
#include <cmath>
#include <memory>

// Here's a basic interface for geometric shapes.
class geometry {
public:
    virtual double area() = 0;
    virtual double perim() = 0;
    virtual ~geometry() {}
};

// For our example we'll implement this interface on
// rect and circle types.
class rect : public geometry {
private:
    double width, height;
public:
    rect(double w, double h) : width(w), height(h) {}
    double area() override {
        return width * height;
    }
    double perim() override {
        return 2*width + 2*height;
    }
};

class circle : public geometry {
private:
    double radius;
public:
    circle(double r) : radius(r) {}
    double area() override {
        return M_PI * radius * radius;
    }
    double perim() override {
        return 2 * M_PI * radius;
    }
};

// If a variable has an interface type, then we can call
// methods that are in the named interface. Here's a
// generic measure function taking advantage of this
// to work on any geometry.
void measure(const std::shared_ptr<geometry>& g) {
    std::cout << g->area() << std::endl;
    std::cout << g->perim() << std::endl;
}

cilk_int main() {
    auto r = std::make_shared<rect>(3, 4);
    auto c = std::make_shared<circle>(5);

    // The circle and rect struct types both
    // implement the geometry interface so we can use
    // instances of these structs as arguments to measure.
    measure(r);
    measure(c);

    return 0;
}