无穷数的定义

// 定义一个求有符号的无穷大的宏  
#define SIGN_INFINITELY_GREAT(T) ((0x1<<8*sizeof(T)-1)-1)  
// 定义一个求有符号的无穷小的宏  
#define SIGN_INFINITELY_SMALL(T) (0x1<<(8*sizeof(T)-1))  
// 定义INT型的无穷大值  
#define INT_INFINITELY_GREATE SIGN_INFINITELY_GREAT(int)  
// 定义INT型的无穷小值  
#define INT_INFINITELY_SMALL SIGN_INFINITELY_SMALL(int)