判断浮点数是否相等

#include <iostream>
#include <cmath>

using namespace std;

int main(int argc, char **argv)
{
    double a = 0.0;
    double b = 0.0;

    std::cout << "Please input a: " << std::endl;
    std::cin >> a;

    std::cout << "Please input b: " << std::endl;
    std::cin >> b;

    if(fabs(a -b) > 0.000001)
    {
        std::cout << "XXXX a != b " << std::endl;
    }
    else
    {
        std::cout << "XXXX a == b" << std::endl;
    }

    return 0;
}