我在论坛上发现了一个问题,我决定写一个快速代码。我决定借此机会自学有关重载比较运算符的问题。不幸的是,我似乎犯了一个错误。
我试图与Line
类中的Quadrilateral
对象进行比较。我不断收到Line
是二元运算符<
的无效操作数的错误。我试着向前声明重载的运算符,但这似乎没有帮助。任何人都可以提出比较不起作用的原因吗?非常感谢任何帮助:)
(重载的运算符函数是代码中的最后一个函数。实际比较发生在Quadrilateral
类)
#include <iostream>
#include <vector>
#include <cmath>
class Point {
private:
int x, y;
public:
Point(): x(0), y(0) {}
Point(int x, int y): x(x), y(y) {}
int getX() const { return x; }
int getY() const { return y; }
friend std::ostream& operator<<(std::ostream& stream, const Point& pt);
};
class Line {
private:
Point pt1, pt2;
public:
Line(): pt1(0,0), pt2(0,1) {}
Line(const Point& pt1, const Point& pt2): pt1(pt1), pt2(pt2) {}
friend auto operator<(const Line& ln1, const Line& ln2) -> bool;
friend std::ostream& operator<<(std::ostream& stream, const Line& ln);
};
class Quadrilateral {
private:
Point pt1, pt2, pt3, pt4;
public:
Quadrilateral(): pt1(0,0), pt2(0,1), pt3(1,0), pt4(1,1) {}
Quadrilateral(const Point& pt1, const Point& pt2,
const Point& pt3, const Point& pt4): pt1(pt1), pt2(pt2),
pt3(pt3), pt4(pt4) {}
auto getAllLines() const -> std::vector<Line> {
std::vector<Line> quadLines;
Line l1(pt1,pt2), l2(pt2,pt3), l3(pt3,pt4), l4(pt4,pt1);
quadLines.push_back(l1); quadLines.push_back(l2);
quadLines.push_back(l3); quadLines.push_back(l4);
return quadLines;
}
auto longestSide() const -> Line {
Line l1(pt1,pt2), l2(pt2,pt3), l3(pt3,pt4), l4(pt4,pt1);
return (l1 > l2 ? l1 : l2);
}
friend std::ostream& operator<<(std::ostream& stream, const Quadrilateral& q);
};
std::ostream& operator<<(std::ostream& stream, const Point& pt) {
stream << "(" << pt.x << ", " << pt.y << ")";
return stream;
}
std::ostream& operator<<(std::ostream& stream, const Line& ln) {
stream << ln.pt1 << " <-> " << ln.pt2 << std::endl;;
return stream;
}
std::ostream& operator<<(std::ostream& stream, const Quadrilateral& q) {
stream << q.pt1 << "\t" << " <-> " << "\t" << q.pt2 << "\n"
<< " ^" << "\t" << "\t" << " ^" << "\n"
<< " |" << "\t" << "\t" << " |" << "\n"
<< " v" << "\t" << "\t" << " v" << "\n"
<< q.pt4 << "\t" << " <-> " << "\t" << q.pt4 << "\n"
<< std::endl;
return stream;
}
auto operator<(const Line& ln1, const Line& ln2) -> bool {
double ln1_len = sqrt( pow((ln1.pt1.getX() - ln1.pt2.getX()),2) - pow((ln1.pt1.getY() - ln1.pt2.getY()),2) );
double ln2_len = sqrt( pow((ln2.pt1.getX() - ln2.pt2.getX()),2) - pow((ln2.pt1.getY() - ln2.pt2.getY()),2) );
return ln1_len < ln2_len;
}
答案 0 :(得分:2)
我认为return (l1 > l2 ? l1 : l2);
会导致错误。请注意,您在此处使用的是>
,但您只定义了operator<()
。