// virtual.cpp
// An example of virtual functions and dynamic dispatch.
// Taken from an example in the lecture slides for CSE 143.

#include <iostream>
using namespace std;
class person {
public:
    virtual void walk() = 0;
    virtual void run() {cout << "Person running" << endl;}
};
class student : public person {
public:
    void enroll() {cout << "Student enrolls" << endl;}  /* BAD STYLE */
    virtual void walk() {cout << "Student walks" << endl;}
};
class freshman : public student {
public:
    void enroll() {cout << "Freshman enrolls" << endl;}
    virtual void run() {cout << "Freshman runs" << endl;}
};
int main() {
    // COMPILE-TIME ERROR:
    //              "cannot instantiate abstract class person"
    // person paula;
    student* stu = new freshman();
    stu->enroll();
    student sara = *stu;  /* BAD STYLE */
    sara.run();
    person* pp = stu;
    pp->run();
    pp->walk();
    
    // COMPILE-TIME ERROR:
    //              "cannot convert from 'class person*' to 'class freshman*'
    // freshman* fred = pp;
    
    
    // COMPILE-TIME ERROR
    //              Invalid because previous line  is invalid
    // fred->enroll();
    return 0;
}



/*  OUTPUT  (take directly from the output screen)
 *
 * Student enrolls
 * Person running
 * Freshman runs
 * Student walks
 *
 */