*** 自写代码：设置或清除特定的位

#include <iostream>
#include <stdio.h>
using namespace std;
#define BIT(n) (0x1<<n)
template <typename T>
T set_bit (T value, T bit_n)
{
    value |= BIT(bit_n);
    return value;
}
template <typename T>
T clear_bit (T value, T bit_n)
{
    value &= ~BIT(bit_n);
    return value;
}
int main()
{
    int a = 0;
    cout << "Please input a hex to set:" << endl;
    scanf("%x", &a);
    printf ("before: a = 0x%x\n", a);
    printf ("after : a = 0x%x\n", set_bit(a, 3));
    cout << "Please input a hex to clear:" << endl;
    scanf("%x", &a);
    printf ("before: a = 0x%x\n", a);
    printf ("after : a = 0x%x\n", clear_bit(a, 3));
    return 0;
}
}