非常奇怪啊!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[hackerning]

这是一个随机数产生器:
#include "sys\timeb.h"
#include "sys\types.h"
#include "time.h"
#include "iostream.h"

#include "conio.h"
#define alpha 3.95

double init(void);
int random(int x)
{
int ran=0;
static double f=-1.0;
if(f==-1.0)f=init();
else
f=alpha*f*(1.0-f);
return x*f;}

double init(void)
{
double f0;
struct timeb *pr;
for(;;)
{
ftime(pr);
f0=pr->millitm*0.9876543*0.001;
if(f0<0.001)continue;
break;
}
return f0;
}

void main(void)
{
clrscr();
int s=8;

while(s>=0)
{
cout<<random(8)<<endl;//????????奇怪的现象出现了,当把random函数放到循环体内是,运行的结果会出现NULL POINTER ..的错误提示.
s--;}
/*cout<<random(8)<<endl;//???????去掉循环,连续写几个RANDOM却运行良好,没有错误提示
cout<<random(8)<<endl;
cout<<random(8)<<endl;
cout<<random(8)<<endl;
cout<<random(8)<<endl;
cout<<random(8)<<endl;*/

}
//这是什么原因???????????????????????????????????????????????????????????????????

[柯本]

init(...)中 *pr没有初始内存，它会导致程序时好时外
正确的写法是
struct timeb *pr;
pr = new timeb;
...

delete pr;

或
struct timeb pr;
...
ftime(&pr);
f0=pr.millitm*0.9876543*0.001;
...