编译怪谈

[nyunknown]

代码如下：
#include<iostream.h>
#include<stdlib.h>
#include<time.h>

void main()
{
srand(time(0));
int counter=0;
int magic,guess;
magic=1+rand()%1000;
cout<<"I have a number between 1 and 1000.\n"
<<"Can you guess my number?\n"
<<"Please type your first guess."<<endl;
cin>>guess;
counter++;
while(guess!=magic)
{
if(guess>=magic)
cout<<"Too high,try again.\n";
if(guess<=magic)
cout<<"Too low,try again.\n";
cin>>guess;
counter++;
}
if(counter==10)
cout<<"Ahah! You know the secret.\n";
if(counter>10)
cout<<"You should be able to do better.\n";
if(counter<10)
cout<<"Either you know the secret or you got lucky!"
<<endl;
for(;;);
}
最后一个for循环是用来延时的，可以去掉，
但如果不去掉，编译后执行时，当应该要显示语句Ahah! You know the secret和You should be able to do better.时，它就不会显示出来。这是怎么回事？

另一个问题的代码：
#include<iostream.h>
#include<stdlib.h>
#include<time.h>

int produce_rand_number(void)
{
return 1+rand()%10;
}

void main()
{
int result;
srand(time(0));
for(;;)
{
int number1=produce_rand_number();
int number2=produce_rand_number();

cout<<"how much is "<<number1<<" "
<<"times "<<number2<<"?---(0 to end)"<<endl;
cin>>result;

if(result==0)exit(0);

while(result!=number1*number2)
{
cout<<"No,please try again.\n";
cin>>result;//为什么我输入0点几，如：0.1程序就会进入无限循环

}
cout<<"Very good!"<<endl;
}
}

最后一个BC问题：
用VC在DOS下编程，往往执行后就会立即退出，怎样才能使之延时退出

[nyunknown]

问题1：语句cout<<"Either you know the secret or you got lucky!"
<<endl;
和语句cout<<"Either you know the secret or you got lucky!";
cout<<endl;有什么不同？
问题2：result即使为0也不应该进入无限循环啊

[blue_flash]

问题1 没有结束输出，应改为：
if(counter==10)
cout<<"Ahah! You know the secret.\n";
if(counter>10)
cout<<"You should be able to do better.\n";
if(counter<10)
cout<<"Either you know the secret or you got lucky!"
<<endl;

[blue_flash]

问题1 没有结束输出，应改为：
if(counter==10)
cout<<"Ahah! You know the secret.\n";
if(counter>10)
cout<<"You should be able to do better.\n";
if(counter<10)
cout<<"Either you know the secret or you got lucky!\n"

cout<<endl;

问题2
result 声明为int 所以输入小数，自动取整，（不是四舍五入）
输入0.XXX时 result = 0;

问题3
getchar()

[nyunknown]

没人知道吗？？？

[blue_flash]

输入0.1会运行到这个函数
int istream::getint(char * buffer) // returns length
{
int base, i;
int c;
int fDigit = 0;
int bindex = 1;

if (x_flags & ios::dec)
base = 10;
else if (x_flags & ios::hex)
base = 16;
else if (x_flags & ios::oct)
base = 8;
else
base = 0;

if (ipfx(0))
{
c=bp->sgetc();
for (i = 0; i<MAXLONGSIZ-1; buffer[i] = (char)c,c=bp->snextc(),i++)
{
if (c==EOF)
{
state |= ios::eofbit;
break;
}
if (!i)
{
if ((c=='-') || (c=='+'))
{
bindex++;
continue;
}
}
if ((i==bindex) && (buffer[i-1]=='0'))
{
if (((c=='x') || (c=='X')) && ((base==0) || (base==16)))
{
base = 16; // simplifies matters
fDigit = 0;
continue;
}
else if (base==0)
{
base = 8;
}
}


// now simply look for a digit and set fDigit if found else break

if (base==16)
{
if (!isxdigit(c))
break;
}
else if ((!isdigit(c)) || ((base==8) && (c>'7')))
break;

fDigit++;
}
if (!fDigit)
{
state |= ios::failbit; // <= 运行到这里时，因为不是数字，会设置错误状态，下次在获取输入时因为存在错误状态，直接跳过了，因此，再次接收输入时，必须清除掉错误状态。
while (i--)
{
if(bp->sputbackc(buffer[i])==EOF)
{
state |= ios::badbit;
break;
}
else
state &= ~(ios::eofbit);
}
i=0;
}
// buffer contains a valid number or '\0'
buffer[i] = '\0';
isfx();
}
if (i==MAXLONGSIZ)
{
state |= ios::failbit;
}
return base;
}

[quanxiongwei]

同意nyunknown(unknown)