C# 运算符重载

运算符重载

一提到+ - * / %这种类似的运算符都应该很清楚是什么，但是程序是怎么实现的呢？
程序员也可以使用用户自定义类型的运算符。重载运算符是具有特殊名称的函数，是通过关键字 operator 后跟运算符的符号来定义的。与其他函数一样，重载运算符有返回类型和参数列表。

运算符重载的实现

重载运算符注意几点：

1. 类中重载的方法必须是public公有的

2. 类中定义的重载方法必须是静态的

3. 在运算符前需要加上关键字 operator

class Box
    {
        private int length;      // 长度
        private int breadth;     // 宽度
        private int height;      // 高度

        public int getVolume()
        {
            return length * breadth * height;
        }
        public void setLength(int len)
        {
            length = len;
        }

        public void setBreadth(int bre)
        {
            breadth = bre;
        }

        public void setHeight(int hei)
        {
            height = hei;
        }

        public static Box operator + (Box b,Box c)
        {
            Box box = new Box();
            box.height = b.height + c.height;
            box.length = b.length + c.length;
            box.breadth = b.breadth + c.breadth;
            return box;
        }

        public static Box operator -(Box b, Box c)
        {
            Box box = new Box();
            box.height = b.height - c.height;
            box.length = b.length - c.length;
            box.breadth = b.breadth - c.breadth;
            return box;
        }

        public static Box operator *(Box b, Box c)
        {
            Box box = new Box();
            box.height = b.height * c.height;
            box.length = b.length * c.length;
            box.breadth = b.breadth * c.breadth;
            return box;
        }

        public static Box operator /(Box b, Box c)
        {
            Box box = new Box();
            box.height = b.height / c.height;
            box.length = b.length / c.length;
            box.breadth = b.breadth / c.breadth;
            return box;
        }
    }

使用如下

 	 Box box1 = new Box();
     Box box2 = new Box();
     Box box3 = new Box();
     int volume = 0;

     //box1
     box1.setLength(6);
     box1.setBreadth(7);
     box1.setHeight(5);

     //box2
     box2.setLength(12);
     box2.setBreadth(13);
     box2.setHeight(10);

     volume = box1.getVolume();
     Debug.LogError(volume);

     volume = box2.getVolume();
     Debug.LogError(volume);

     box3 = box1 + box2;
     volume = box3.getVolume();
     Debug.LogError(volume);
     

当上面的代码被编译和执行时，它会产生下列结果：

可重载和不可重载运算符

运算符	描述
+, -, !, ~, ++, –	这些一元运算符只有一个操作数，且可以被重载。
+, -, *, /, %	这些二元运算符只有一个操作数，且可以被重载。
==, !=, <, >, <=, >=	这些比较运算符可以被重载。
&&,ll	这些一元运算符只有一个操作数，且可以被重载。
+=, -=, *=, /=, %=	这些赋值运算符不能被重载。
=, ., ?:, ->, new, is, sizeof, typeof	这些运算符不能被重载。

实例

// 重载 + 运算符来把两个 Box 对象相加
      public static Box operator+ (Box b, Box c)
      {
          Box box = new Box();
          box.length = b.length + c.length;
          box.breadth = b.breadth + c.breadth;
          box.height = b.height + c.height;
          return box;
      }
      
      public static bool operator == (Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length == rhs.length && lhs.height == rhs.height 
             && lhs.breadth == rhs.breadth)
          {
              status = true;
          }
          return status;
      }
      public static bool operator !=(Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length != rhs.length || lhs.height != rhs.height 
              || lhs.breadth != rhs.breadth)
          {
              status = true;
          }
          return status;
      }
      public static bool operator <(Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length < rhs.length && lhs.height 
              < rhs.height && lhs.breadth < rhs.breadth)
          {
              status = true;
          }
          return status;
      }

      public static bool operator >(Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length > rhs.length && lhs.height 
              > rhs.height && lhs.breadth > rhs.breadth)
          {
              status = true;
          }
          return status;
      }

      public static bool operator <=(Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length <= rhs.length && lhs.height 
              <= rhs.height && lhs.breadth <= rhs.breadth)
          {
              status = true;
          }
          return status;
      }

      public static bool operator >=(Box lhs, Box rhs)
      {
          bool status = false;
          if (lhs.length >= rhs.length && lhs.height 
             >= rhs.height && lhs.breadth >= rhs.breadth)
          {
              status = true;
          }
          return status;
      }
      public override string ToString()
      {
          return String.Format("({0}, {1}, {2})", length, breadth, height);
      }