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C++中的“操作符*”没有匹配

operator-overloading c++

Stiven Choking · 技术社区 · 4 年前

class X {
     
   public:
      double getLength(void) {
         return length;
      }
      void setLength( double len ) {
         length = len;
      } 
      
      // Overload + operator to add two Box objects.
     X operator*(X temp){
         X temp1;
         temp1.length = this->length * temp1.length;
         return temp1;
      }
      
      X operator*(int num){
         X temp1;
         temp1.length = this->length * num;
         return temp1; 
      }
      
     X operator+(X temp){ 
         X temp1;
         temp1.length = this->length + temp1.length;
         return temp1; 
      }
      
   private:
      double length;      // Length of a box
      
};

// Main function for the program
int main() {
   X ob1;                // Declare Box1 of type Box
   X ob2;                // Declare Box2 of type Box
   X ob3;                // Declare Box3 of type Box
   double result = 0.0;     // Store the volume of a box here
 
   ob2.setLength(6.0);  
   ob3.setLength(12.0);  
 
   ob1 = ob2 + 2*ob3;
   ob1 = ob2*2 + ob3;
   ob1 = (ob2 + 2) *ob3;
 
   cout << "length of Box  : " << ob1.getLength() <<endl;

   return 0;
}

main.cpp: In function 'int main()':
main.cpp:48:17: error: no match for 'operator*' (operand types are 'int' and 'X')
    ob1 = ob2 + 2*ob3;
                ~^~~~
main.cpp:50:15: error: no match for 'operator+' (operand types are 'X' and 'int')
    ob1 = (ob2 + 2) *ob3;
           ~~~~^~~
main.cpp:27:8: note: candidate: 'X X::operator+(X)'
      X operator+(X temp){

2 回复 | 直到 4 年前

Some programmer dude 4 年前

ob3 * 2:;  // Fine: Calls ob3.operator*(2)
2 * ob3;   // Not fine, there's no operator* function which takes an int on the left-hand side

您可以使用

X operator*(int a, X b)
{
    return b * a;  // Calls b.operator*(a)
}

int

2 * ob3;  // Fine: Calls operator+(2, ob3)

this operator overloading canonical implementaiton reference operator*= operator* *=

463035818_is_not_an_ai 4 年前

operator* int * X operator+ X + int X * int X * X X + X

const

#include <iostream>

class X {         
   public:
      X(double length=0.0) : length(length) {}   // <- converting constructor
      double getLength() const {             // <- const !!!
         return length;
      }
      void setLength(double len) {
         length = len;
      } 
   private:
      double length;      // Length of a box          
};

X operator*(const X& a,const X& b){
    return {a.getLength() * b.getLength()};
}
     
X operator+(const X& a,const X& b){ 
    return {a.getLength() + b.getLength()}; 
}

int main() {
   X ob2{6.0};
   X ob3{12.0};
   X ob3;
 
   ob1 = ob2 + 2*ob3;
   ob1 = ob2*2 + ob3;
   ob1 = (ob2 + 2) *ob3;
 
   std::cout << "length of Box  : " << ob1.getLength() << std::endl;
}

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