根据资料，C++浮点数计算时存在精度误差，在一些情况下比较浮点数可能应使用特定的比较函数；

#include "stdafx.h"
#include<iostream>

using namespace std;

#define EPS 1e-9

int main(int argc, char* argv[])
{

	double a = 0.3;
	double b = 0.1 + 0.2;

	cout << "a = " << a << endl;
	cout << "b = " << b << endl;
	cout << "a-b = " << a - b << endl;

	if (abs(a - b) < EPS)  // 比较浮点数需考虑精度误差
	{
		cout << "a and b are the same" << endl;
	}
	return 0;
}