使用运算符重载时 C++ 意外输出

Question

我正在尝试遍历“圆”结构（基本上是二叉树）。每个圆都有一个 centerX、centerY、radius 和两个叶节点。这些叶子要么都为空，要么都不为空。永远不会有一个null和一个not null。

我正在使用运算符重载使用 SVG 文件格式将圆打印到输出流。以下是相关代码：

circle.h:

#include <set>
#include <iostream>

using namespace std;

class Circle {
 private:
  double centerX, centerY, radius;
  Circle* c1;
  Circle* c2;
  
 public:
  static const int PAGE_DIMENSION = 200;
  static const int DEFAULT_MAX_RADIUS = 15;
  
  Circle( double x, double y, double radius, Circle* r1,  Circle* r2 );
  Circle( double x, double y, double radius );
  Circle();
  
  int isLeaf() const;
  double getCenterX() const;
  double getCenterY() const;
  double area() const;
  double getRadius() const;
  Circle* getFirstSubcircle() const;
  Circle* getSecondSubcircle() const;
  
  bool operator<( Circle& other );
  Circle* operator()( double x_in, double y_in);
  Circle& operator=( Circle& rhs);
  Circle* operator,( Circle& other ); 
  double distance( Circle& rhs );

  // THESE FUNCTIONS ARE NOT CLASS MEMBERS
  // THEY ARE DEFINED OUTSIDE OF THE CLASS
  // BUT REQUIRE ACCESS TO PRIVATE FIELDS
  friend ostream& operator<<(ostream& osInput, Circle& circle);
  friend ostream& operator/(ostream& osInput, Circle& circle);
  friend Circle* reduce( set<Circle*>&  circles);
};

circle.cpp:

#include <math.h>
#include <time.h>
#include <iostream>
#include <algorithm>
#include <stdlib.h>
#include <set>
#include <fstream>
#include "circle.h"


using namespace std;

  Circle::Circle( double x, double y, double radius, Circle* r1,  Circle* r2 )
  {
      centerX = x;
      centerY = y;
      this->radius = radius;
      c1 = r1;
      c2 = r2;
  }

  Circle::Circle( double x, double y, double radius )
  {
      centerX = x;
      centerY = y;
      this->radius = radius;
  }

  Circle::Circle()
  {
      srand(time(0));
      int randomX = rand() % (PAGE_DIMENSION + 1);
      int randomY = rand() % (PAGE_DIMENSION + 1);
      int randomRadius = rand() % DEFAULT_MAX_RADIUS + 1;
      centerX = randomX;
      centerY = randomY;
      radius = randomRadius;
  }

  Circle* Circle::getFirstSubcircle() const
  {
      return c1;
  }

  Circle* Circle::getSecondSubcircle() const
  {
      return c2;
  }

  int Circle::isLeaf() const
  {
      if (c1 == NULL && c2 == NULL) {
          return 1;
      }

      return 0;
  }

  ostream& operator/(ostream& osInput, Circle& circle)
  {
      if (circle.isLeaf()) {
          osInput << " <circle cx=\"" << circle.centerX << "\" cy=\"" << circle.centerY <<"\" radius=\"" << circle.radius << "\" style=\"fill:blue;stroke:black;stroke-width:.05;fill-opacity:.1;stroke-opacity:.9\"/>\n";
      }
      else {
          osInput << " <circle cx=\"" << circle.centerX << "\" cy=\"" << circle.centerY <<"\" radius=\"" << circle.radius << "\" style=\"fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5\"/>\n";
          Circle* firstCircle = circle.getFirstSubcircle();
          Circle* secondCircle = circle.getSecondSubcircle();
          osInput / *firstCircle;
          osInput / *secondCircle;
      }
  }

test.cpp:

#include <iostream>
#include <fstream>
#include <set>
#include <string>
#include <stdlib.h>
#include "circle.h"

using namespace std;

int main( int argc, char** argv ) {
    Circle* circ2_1 = new Circle(45, 65, 3);
    Circle* circ2_2 = new Circle(56, 55, 3);
    Circle* circ2 = new Circle(11, 21, 8, circ2_1, circ2_2);
    Circle* circ3 = new Circle(7, 7, 7);
    Circle* circ4 = new Circle(10, 25, 11, circ2, circ3);
    cout / *circ4;
}

当我运行上面的代码时，我得到以下输出：

 <circle cx="10" cy="25" radius="11" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
 <circle cx="11" cy="21" radius="8" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
 <circle cx="45" cy="65" radius="3" style="fill:blue;stroke:black;stroke-width:.05;fill-opacity:.1;stroke-opacity:.9"/>
 <circle cx="56" cy="55" radius="3" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>

以下输出是我所期望的（基于 main 中的代码）：

 <circle cx="10" cy="25" radius="11" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
<circle cx="11" cy="21" radius="8" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
 <circle cx="45" cy="65" radius="3" style="fill:blue;stroke:black;stroke-width:.05;fill-opacity:.1;stroke-opacity:.9"/>
 <circle cx="56" cy="55" radius="3" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
 <circle cx="7" cy="7" radius="7" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>

如果我将 circle.cpp 中“ostream& operator/”函数中的最后几行代码切换为以下代码：

osInput / *secondCircle;
osInput / *firstCircle;

输出将是：

 <circle cx="10" cy="25" radius="11" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>
 <circle cx="7" cy="7" radius="7" style="fill:yellow;stroke:black;stroke-width:.05;fill-opacity:.0;stroke-opacity:.5"/>

同样，这不是我所期待的。问题似乎是它只是将代码中列出的第一个圆圈附加到 ostream，无论它是首先出现的“firstCircle”还是“secondCircle”。我认为它应该产生我期望的输出是错误的吗？任何指向我正确方向的想法都将不胜感激，因为我已经尝试了我能想到的一切。

Answer 1

对于 3 参数 Circle 构造函数，您无需初始化 c1 或 c2 成员。当您稍后尝试取消引用这些值（可能是崩溃）时，这将是未定义的行为。

使用运算符重载时 C++ 意外输出

C++ unexpected output when using operator overloading

c++

operator-overloading

ostream