#include <stdio.h>

typedef struct Class{
　void (*Method1)(struct Class*);
　void (*Method2)(struct Class*);
　int field1;
　int field2;
}Class;

static void Class_Method1(Class* this){
　printf("%d\n",this->field1);
}

static void Class_Method2(Class* this){
　printf("%d\n",this->field2);
}

static Class* Class_Constractor(){
　Class* this = (Class*)malloc(sizeof(Class));
　this->Method1 = Class_Method1;
　this->Method2 = Class_Method2;
　this->field1 = 10;
　this->field2 = 20;
　return this;
}

static void SubClass_Method1(Class* this){
　printf("%d\n",this->field1+this->field2);
}

static void SubClass_Method2(Class* this){
　printf("%d\n",this->field1-this->field2);
}

static Class* SubClass_Constractor(){
　Class* this = Class_Constractor();
　this->Method1 = SubClass_Method1;
　this->Method2 = SubClass_Method2;
　return this;
}

int main(){

　Class* this = Class_Constractor();
　this->Method1(this);
　this->Method2(this);
　free(this);

　this = SubClass_Constractor();
　this->Method1(this);
　this->Method2(this);
　free(this);

　return 0;

}