c vs c++ in strcut and class

c vs c++ in strcut and class

总习惯用c的用法，现在学习C++，老爱拿来比较。声明我用的是g++4.2.1 SUSE Linux。看例子吧

#include <iostream>
#include <cstring>
#include <string>

using namespace std;

enum zoo_obj_kind{
        null    = 0,
#define null    null
        no      = 0,
#define no      no
        animal  = 2,
#define animal animal
        plant   = 4,
#define plant   plant
        others  = 8
#define others  others

};

struct zoo_obj{
        zoo_obj_kind zo_kind;
        char name [40];
};
class zoo_obj_1{
        zoo_obj_kind zo_kind;
        char    name [40];

};

int main(void){

        cout << "struct :" << sizeof(struct zoo_obj) << endl;
        cout << "clsas :" << sizeof( zoo_obj_1) << endl;


}

结果

struct size:44
clsas size:44

-------------------------------

#include <iostream>
#include <cstring>
#include <string>

using namespace std;

enum zoo_obj_kind{
        null    = 0,
#define null    null
        no      = 0,
#define no      no
        animal  = 2,
#define animal animal
        plant   = 4,
#define plant   plant
        others  = 8
#define others  others

};

struct zoo_obj{
        zoo_obj_kind zo_kind;
        char name [40];
        void (*say)(struct zoo_obj *);
};
void say(struct zoo_obj *obj){
        if(!obj) {
                printf("null
");
                return ;
        }
        printf("name:%s
",obj->name);

}
class zoo_obj_1{
        zoo_obj_kind zo_kind;
        char    name [40];
        void say(zoo_obj_1 &obj){
                cout << "name:" << name << endl;

        }
};

int main(void){

        cout << "struct :" << sizeof(struct zoo_obj) << endl;
        cout << "clsas :" << sizeof( zoo_obj_1) << endl;


}

结果

struct size:48
clsas size:44

呵呵，有意思吧，在class中成员函数不占空间。下面你看看他们有多像

 

#include <iostream>
#include <cstring>
#include <string>

using namespace std;

enum zoo_obj_kind{
        null    = 0,
#define null    null
        no      = 0,
#define no      no
        animal  = 2,
#define animal animal
        plant   = 4,
#define plant   plant
        others  = 8
#define others  others

};

struct zoo_obj{
        zoo_obj_kind zo_kind;
        char name [40];
        void (*say)(struct zoo_obj &);
};
void say(struct zoo_obj &obj){
        printf("name:%s
",obj.name);

}
class zoo_obj_1{
        public:
        zoo_obj_kind zo_kind;
        char    name [40];
        void say(){cout << "name:" << name << endl;}
        void say(zoo_obj_1 &obj){cout << "name:" << obj.name << endl;}
};

typedef struct zoo_obj s_zoo_obj;
typedef zoo_obj_1 c_zoo_obj;

int main(void){

        s_zoo_obj s_obj = {animal,"dog",say};
        zoo_obj_1 c_obj = {animal,"cat"};

        cout << "struct size:" << sizeof(struct zoo_obj) << endl;
        cout << "clsas size:" << sizeof( zoo_obj_1) << endl;

        s_obj.say(s_obj);
        c_obj.say(c_obj);

}

结果

struct size:48
clsas size:44
name:dog
name:cat

这是同时使用了引用，那么指针呢。struct的指针当然没有问题，那么class的指针呢？看看代码

#include <iostream>
#include <cstring>
#include <string>

using namespace std;

enum zoo_obj_kind{
        null    = 0,
#define null    null
        no      = 0,
#define no      no
        animal  = 2,
#define animal animal
        plant   = 4,
#define plant   plant
        others  = 8
#define others  others

};

struct zoo_obj{
        zoo_obj_kind zo_kind;
        char name [40];
        void (*say)(struct zoo_obj *);
};
void say(struct zoo_obj *obj){
        !obj
        ? printf("null
")
        : printf("name:%s
",obj->name);

}
class zoo_obj_1{
        public:
        zoo_obj_kind zo_kind;
        char    name [40];
        void say(){cout << "name:" << name << endl;}
        void say(zoo_obj_1 *obj){
                !obj
                ? cout << "null
"
                : cout << "name:" << obj->name << endl;
        }
};

typedef struct zoo_obj s_zoo_obj;
typedef zoo_obj_1 c_zoo_obj;

int main(void){

        s_zoo_obj s_obj = {animal,"dog",say};
        zoo_obj_1 c_obj = {animal,"cat"};

        cout << "struct size:" << sizeof(struct zoo_obj) << endl;
        cout << "clsas size:" << sizeof( zoo_obj_1) << endl;

        s_obj.say(&s_obj);
        c_obj.say(&c_obj);

        s_obj.say(NULL);
        c_obj.say(NULL);

}

哈哈，结果仍然是

 

struct size:48
clsas size:44
name:dog
name:cat

更高级的特性呢？

比如在继承，接口。。。

个人认为C的这类名词没有，但他确实能出色的实现诸如此类的功能，而且更直观。可能是我的C++还不行吧。C高效和简单直观是没得说的。