在C / C ++中进行浮点和双重比较的最有效方法是什么？
在这里，我们将看到如何使用C或C++比较两个浮点数据或两个双精度数据。浮点/双精度比较不同于整数比较。
要比较两个浮点或双精度值，我们必须考虑比较的精度。例如，如果两个数字分别为3.1428和3.1415，则精度达到0.01时它们是相同的，但此后，它们像0.001一样不相同。
为了使用此标准进行比较，我们将在从另一个浮点数减去一个浮点数后找到绝对值，然后检查结果是否小于精度值。由此我们可以确定它们是否相等。
示例
#include <iostream>
#include <cmath>
using namespace std;
bool compare_float(float x, float y, float epsilon = 0.01f){
if(fabs(x - y) < epsilon)
return true; //they are same
return false; //they are not same
}
bool compare_float(double x, double y, double epsilon = 0.0000001f){
if(fabs(x - y) < epsilon)
return true; //they are same
return false; //they are not same
}
int main() {
float x, y;
x = 22.0f/7.0f;
y = 3.1415f;
if(compare_float(x, y)){
cout << "They are equivalent" << endl;
} else {
cout << "They are not equivalent" << endl;
}
if(compare_float(x, y, 0.001f)){
cout << "They are equivalent" << endl;
} else {
cout << "They are not equivalent" << endl;
}
double a, b;
a = 2.03547415;
b = 2.03547428;
if(compare_float(a, b)){
cout << "They are equivalent" << endl;
} else {
cout << "They are not equivalent" << endl;
}
if(compare_float(a, b, 0.000001f)){
cout << "They are equivalent" << endl;
} else {
cout << "They are not equivalent" << endl;
}
}输出结果
They are equivalent They are not equivalent They are not equivalent They are equivalent