[C++] Polymorphism

http://teddy-chen-tw.blogspot.com/2012/01/3polymorphism.html
http://monkeycoding.com/?p=936

#include &ltiostream&gt
using namespace std;

class animal {
public:
    virtual void f1() = 0;
    virtual void f2() = 0;
    virtual void f3() = 0;
};

class cat : public animal {
public:
    void f1() {
        cout << "cat's f1" << endl;
    }

    void f2() {
        cout << "cat's f2" << endl;
    }

    void f3() {
        cout << "cat's f3" << endl;
    }
};

class dog : public animal {
public:
    void f1() {
        cout << "dog's f1" << endl;
    }

    void f2() {
        cout << "dog's f2" << endl;
    }
    
    void f3() {
        cout << "dog's f3" << endl;
    }
};


int main() {
  animal *a = new dog;

  a->f1();
}

C 版本的多型

#include <stdio.h>
#include <string.h>

struct animal {
    void (*f1)(void);
    void (*f2)(void);
    void (*f3)(void);
};


void dog_f1(void) { printf("dog's f1\n"); }
void dog_f2(void) { printf("dog's f2\n"); }
void dog_f3(void) { printf("dog's f3\n"); }

void cat_f1(void) { printf("cat's f1\n"); }
void cat_f2(void) { printf("cat's f2\n"); }
void cat_f3(void) { printf("cat's f3\n"); }

struct animal dog = {
    dog_f1,
    dog_f2,
    dog_f3,
};

struct animal cat = {
    cat_f1,
    cat_f2,
    cat_f3,
};

int main(int argc, char **argv)
{
    struct animal *a;
    
    if (strcmp(argv[1], "dog") == 0)
        a = &dog;
    else if (strcmp(argv[1], "cat") == 0)
        a = &cat;
    
    a->f1();
    
    return 0;
}