2009-10-26c语言日记（预处理）

/*##运算符*/#include<stdio.h>#define XNAME(n) x##n#define PRINT_XN(n) printf("x" #n" = %d/n",x##n)int main(void){int XNAME(1) = 14;//x1 = 14int XNAME(2) = 20;//x2 = 20PRINT_XN(1);PRINT_XN(2);return 0;}

 

2009-10-26

#include<stdio.h>#define TWO 2#define OW "Consistency is the last refuge of the unimagina/tive. -Oscar Wilde"#define FOUR TWO*TWO#define PX printf("X is %d./n",x)#define PMT "X is %d./n"int main(void){int x = TWO;PX;x = FOUR;printf(PMT,x);printf("%s/n",OW);printf("TWO:OW/n");return 0;}

 

const int LIM = 50;
const int LIM2 = 2 * LIM;/*error*/
const int LIM2 = 2 * LIMIT;
0 不是字符'0'，而是ascii码表中的'/0'，也就是字符串结束符。
/*#x字符串化*/

#include<stdio.h>#define PSQR(x) printf("The square of "#x" is %d./n",((x)*(x)))int main(void){int y = 5;PSQR(y);PSQR(2 + 4);return 0;}

#ifdef MAVIS
 #include "horse.h"
 #define STABLES 5
#else
 #include "cow.h"
 #define STABLES 15
#endif

#include<stdio.h>#define JUST_CHECKING#define LIMIT 4int main(void){int i;int total = 0;for(i = 1; i <= LIMIT; i++){total += 2 * i * i + 1;#ifdef JUST_CHECKINGprintf("i=%d ,running total= %d/n",i,total);#endif}printf("Grand total = %d/n",total);return 0;}

 

ifndef SIZE//如果没定义SIZE
 #define SIZE 100
#endif

#if SYS == 1
 #include "ipmpc.h"
#elif SYS == 2
 #include "vax.h"
#elif SYS == 3
 #include "mac.h"
#else
 #include "general.h"
#endif