函数类型错误C++

Question

我正在创建一个类来打印一个点，比较两个点以查看它们是否相等，并使用单独的方法找出两个点之间的距离。找到两点之间的距离的方法给了我一个类型错误，我不知道为什么。

#include <iostream> 
using namespace std; 

class Point 
{//in C++ stuff is private by default 

public: 
    Point() { double x = 0; double y = 0; } 
Point (double a, double b) { x = a; y = b; } 

void print() { cout << "(" << x << "," << y << ")\n" << endl; } 

double getX() { return x; }; 
double getY() { return y; }; 

bool compare(Point other) { return (x == other.x && y == other.y); } 

void setX(double a) 
{if (a >= 0) 
    {x = a;}}; 

void setY(double b) 
{if (b >= 0) 
    {y = b;}}; 

double distance(Point point1, Point point2) 
{ 
return(sqrt (pow (point1.getX-point2.getX,2) + pow(point1.getY-point2.getY,2))); 
}; 

private: 
    double x, y; 
}; 


bool Compare(Point a, Point b) { return (a.getX() == b.getX()) && (b.getY() == a.getY()); } 


int main() 
{ 
    Point p1(5,1); 
    Point p2; 

    p2.setX(2); 
    p2.setY(5); 

    p1.print(); 
    p2.print(); 

    p1.getX(); 
    p1.getY(); 

    p2.getX(); 
    p2.getY(); 

    p1.setX(3.5); 
    p1.setY(9); 

    p1.print(); 


     p1.compare(p2); 
    //or p2.equals(p1); 
     distance(p1, p2); 

     cout << "This distance b/w p1 & p2 is:" << distance (p2, p1) << endl; 

} 

Answer 1

你必须通过每个名称后添加()调用的方法getX和getY：

return(sqrt(pow(point1.getX()-point2.getX(),2) + pow(point1.getY()-point2.getY(),2))); 

否则你将被减去函数指针，这是不允许的。

Answer 2

用类替换distance函数。在你的情况下std::distance被调用。并且尽量不要在你的代码中使用using namespace std;。

Answer 3

#include <iostream> 
#include <math.h> 
using namespace std; 

class Point 
{//in C++ stuff is private by default 

public: 
    Point() { double x = 0; double y = 0; } 
Point (double a, double b) { x = a; y = b; } 

void print() { cout << "(" << x << "," << y << ")\n" << endl; } 

double getX() { return x; }; 
double getY() { return y; }; 

bool compare(Point other) { return (x == other.x && y == other.y); } 

void setX(double a) 
{if (a >= 0) 
    {x = a;}}; 

void setY(double b) 
{if (b >= 0) 
    {y = b;}}; 

static double distance1(Point point1, Point point2) 
{ 
return(sqrt (pow (point1.getX()-point2.getX(),2) + pow(point1.getY()-point2.getY(),2))); 
}; 

private: 
    double x, y; 
}; 


bool Compare(Point a, Point b) { return (a.getX() == b.getX()) && (b.getY() == a.getY()); } 


int main() 
{ 
    Point p1(5,1); 
    Point p2; 

    p2.setX(2); 
    p2.setY(5); 

    p1.print(); 
    p2.print(); 

    p1.getX(); 
    p1.getY(); 

    p2.getX(); 
    p2.getY(); 

    p1.setX(3.5); 
    p1.setY(9); 

    p1.print(); 


     p1.compare(p2); 
    //or p2.equals(p1); 
     //distance(p1, p2); 

     cout << "This distance b/w p1 & p2 is:" << Point::distance1 (p2, p1) << endl; 

}