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分类: C/C++

2011-12-13 15:07:09

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
  1. #include <iostream>
  2. #include <cstring>
  3. #include <string>

  4. using namespace std;

  5. enum zoo_obj_kind{
  6.         null = 0,
  7. #define null null
  8.         no = 0,
  9. #define no no
  10.         animal = 2,
  11. #define animal animal
  12.         plant = 4,
  13. #define plant plant
  14.         others = 8
  15. #define others others

  16. };

  17. struct zoo_obj{
  18.         zoo_obj_kind zo_kind;
  19.         char name [40];
  20. };
  21. class zoo_obj_1{
  22.         zoo_obj_kind zo_kind;
  23.         char name [40];

  24. };

  25. int main(void){

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


  28. }
结果
  1. struct size:44
  2. clsas size:44
-------------------------------
  1. #include <iostream>
  2. #include <cstring>
  3. #include <string>

  4. using namespace std;

  5. enum zoo_obj_kind{
  6.         null = 0,
  7. #define null null
  8.         no = 0,
  9. #define no no
  10.         animal = 2,
  11. #define animal animal
  12.         plant = 4,
  13. #define plant plant
  14.         others = 8
  15. #define others others

  16. };

  17. struct zoo_obj{
  18.         zoo_obj_kind zo_kind;
  19.         char name [40];
  20.         void (*say)(struct zoo_obj *);
  21. };
  22. void say(struct zoo_obj *obj){
  23.         if(!obj) {
  24.                 printf("null\n");
  25.                 return ;
  26.         }
  27.         printf("name:%s\n",obj->name);

  28. }
  29. class zoo_obj_1{
  30.         zoo_obj_kind zo_kind;
  31.         char name [40];
  32.         void say(zoo_obj_1 &obj){
  33.                 cout << "name:" << name << endl;

  34.         }
  35. };

  36. int main(void){

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


  39. }
结果
  1. struct size:48
  2. 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

  1. #include <iostream>
  2. #include <cstring>
  3. #include <string>

  4. using namespace std;

  5. enum zoo_obj_kind{
  6.         null = 0,
  7. #define null null
  8.         no = 0,
  9. #define no no
  10.         animal = 2,
  11. #define animal animal
  12.         plant = 4,
  13. #define plant plant
  14.         others = 8
  15. #define others others

  16. };

  17. struct zoo_obj{
  18.         zoo_obj_kind zo_kind;
  19.         char name [40];
  20.         void (*say)(struct zoo_obj &);
  21. };
  22. void say(struct zoo_obj &obj){
  23.         printf("name:%s\n",obj.name);

  24. }
  25. class zoo_obj_1{
  26.         public:
  27.         zoo_obj_kind zo_kind;
  28.         char name [40];
  29.         void say(){cout << "name:" << name << endl;}
  30.         void say(zoo_obj_1 &obj){cout << "name:" << obj.name << endl;}
  31. };

  32. typedef struct zoo_obj s_zoo_obj;
  33. typedef zoo_obj_1 c_zoo_obj;

  34. int main(void){

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

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

  39.         s_obj.say(s_obj);
  40.         c_obj.say(c_obj);

  41. }
结果
  1. struct size:48
  2. clsas size:44
  3. name:dog
  4. 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
  1. #include <iostream>
  2. #include <cstring>
  3. #include <string>

  4. using namespace std;

  5. enum zoo_obj_kind{
  6.         null = 0,
  7. #define null null
  8.         no = 0,
  9. #define no no
  10.         animal = 2,
  11. #define animal animal
  12.         plant = 4,
  13. #define plant plant
  14.         others = 8
  15. #define others others

  16. };

  17. struct zoo_obj{
  18.         zoo_obj_kind zo_kind;
  19.         char name [40];
  20.         void (*say)(struct zoo_obj *);
  21. };
  22. void say(struct zoo_obj *obj){
  23.         !obj
  24.         ? printf("null\n")
  25.         : printf("name:%s\n",obj->name);

  26. }
  27. class zoo_obj_1{
  28.         public:
  29.         zoo_obj_kind zo_kind;
  30.         char name [40];
  31.         void say(){cout << "name:" << name << endl;}
  32.         void say(zoo_obj_1 *obj){
  33.                 !obj
  34.                 ? cout << "null\n"
  35.                 : cout << "name:" << obj->name << endl;
  36.         }
  37. };

  38. typedef struct zoo_obj s_zoo_obj;
  39. typedef zoo_obj_1 c_zoo_obj;

  40. int main(void){

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

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

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

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

  49. }
哈哈,结果仍然是

  1. struct size:48
  2. clsas size:44
  3. name:dog
  4. 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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