函数名: matherr 
 功  能: 用户可修改的数学错误处理程序 
 用  法: #include<math.h> 
         int matherr(struct exception *e); 
 程序例: 
/* This is a user-defined matherr function that prevents 
    any error messages from being printed. */ 
#include<math.h>
int matherr(struct exception *a) 
 { 
    return 1; 
 }