Question

numeric_limits问题

#include <limits>
#include <iostream>
using std::cout;
using std::endl;
using std::numeric_limits;
int main() {
cout << endl
<< "The range for type short is from "
<< numeric_limits<short>::min()
<< " to "
<< numeric_limits<short>::max();
return 0;
}

提示：error C2653: 'numeric_limits<short>' : is not a class or namespace name
但当我用using namespace std;代替“using std::cout;
using std::endl;
using std::numeric_limits;
”时就能运行正确了，为什么？
我在做一个题目：创建一个程序，输出由8个随机大小的字母或数字组成的密码。允许输入重复的字符。代码如下：
#include <iostream>
#include <cctype>
#include <limits>
#include <ctime>
#include<cstdlib>

using namespace std;

int main() {
const int chars_in_password= 8;
char ch = 0;
srand(static_cast<unsigned int>(time(NULL)));

cout << "Your password is: ";

// We have to read at least one character - even if it's '#' - so do-while is best
for (int i = 0 ; i< chars_in_password ; i++)
while(true)
{
// Character code is a random value between the minimum and maximum for type char
ch = numeric_limits<char>::min()+((numeric_limits<char>::max()-numeric_limits<char>::min())*rand())/RAND_MAX;
if(!isalnum(ch))
continue;
cout << ch;
break;
}
cout << endl;
return 0;
}
目前问题是：能正常运行，但最后输入的不是字母，而是乱码，何解？

Answer 1

问题补充：我开始以为 std::numeric_limits