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>
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#include <cstring>
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#include <string>
-
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using namespace std;
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enum zoo_obj_kind{
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null = 0,
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#define null null
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no = 0,
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#define no no
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animal = 2,
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#define animal animal
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plant = 4,
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#define plant plant
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others = 8
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#define others others
-
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};
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struct zoo_obj{
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zoo_obj_kind zo_kind;
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char name [40];
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};
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class zoo_obj_1{
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zoo_obj_kind zo_kind;
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char name [40];
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};
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int main(void){
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cout << "struct :" << sizeof(struct zoo_obj) << endl;
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cout << "clsas :" << sizeof( zoo_obj_1) << endl;
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-
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}
结果
- struct size:44
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clsas size:44
-------------------------------
- #include <iostream>
-
#include <cstring>
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#include <string>
-
-
using namespace std;
-
-
enum zoo_obj_kind{
-
null = 0,
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#define null null
-
no = 0,
-
#define no no
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animal = 2,
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#define animal animal
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plant = 4,
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#define plant plant
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others = 8
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#define others others
-
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};
-
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struct zoo_obj{
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zoo_obj_kind zo_kind;
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char name [40];
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void (*say)(struct zoo_obj *);
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};
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void say(struct zoo_obj *obj){
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if(!obj) {
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printf("null\n");
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return ;
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}
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printf("name:%s\n",obj->name);
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}
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class zoo_obj_1{
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zoo_obj_kind zo_kind;
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char name [40];
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void say(zoo_obj_1 &obj){
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cout << "name:" << name << endl;
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}
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};
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int main(void){
-
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cout << "struct :" << sizeof(struct zoo_obj) << endl;
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cout << "clsas :" << sizeof( zoo_obj_1) << endl;
-
-
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}
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;
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char name [40];
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void (*say)(struct zoo_obj &);
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};
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void say(struct zoo_obj &obj){
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printf("name:%s\n",obj.name);
-
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}
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class zoo_obj_1{
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public:
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zoo_obj_kind zo_kind;
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char name [40];
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void say(){cout << "name:" << name << endl;}
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void say(zoo_obj_1 &obj){cout << "name:" << obj.name << endl;}
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};
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typedef struct zoo_obj s_zoo_obj;
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typedef zoo_obj_1 c_zoo_obj;
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int main(void){
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s_zoo_obj s_obj = {animal,"dog",say};
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zoo_obj_1 c_obj = {animal,"cat"};
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cout << "struct size:" << sizeof(struct zoo_obj) << endl;
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cout << "clsas size:" << sizeof( zoo_obj_1) << endl;
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s_obj.say(s_obj);
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c_obj.say(c_obj);
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}
结果
- struct size:48
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clsas size:44
-
name:dog
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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{
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zoo_obj_kind zo_kind;
-
char name [40];
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void (*say)(struct zoo_obj *);
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};
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void say(struct zoo_obj *obj){
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!obj
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? printf("null\n")
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: printf("name:%s\n",obj->name);
-
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}
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class zoo_obj_1{
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public:
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zoo_obj_kind zo_kind;
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char name [40];
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void say(){cout << "name:" << name << endl;}
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void say(zoo_obj_1 *obj){
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!obj
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? cout << "null\n"
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: cout << "name:" << obj->name << endl;
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}
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};
-
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typedef struct zoo_obj s_zoo_obj;
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typedef zoo_obj_1 c_zoo_obj;
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int main(void){
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s_zoo_obj s_obj = {animal,"dog",say};
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zoo_obj_1 c_obj = {animal,"cat"};
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cout << "struct size:" << sizeof(struct zoo_obj) << endl;
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cout << "clsas size:" << sizeof( zoo_obj_1) << endl;
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s_obj.say(&s_obj);
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c_obj.say(&c_obj);
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s_obj.say(NULL);
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c_obj.say(NULL);
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}
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。
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