double cast operator : overload cast operator « Operator Overloading « C++ Tutorial

1. C++ Tutorial
2. Operator Overloading
3. overload cast operator

#include <iostream>
using namespace std;

class Power {
  double b;
  int e;
  double val;
public:
    Power(double base, int exp)
    {
      b = base;
      e = exp;
      val = 1;
      if(exp==0)
         return;
      for( ; exp>0; exp--)
         val = val * b;
    }

  Power operator+(Power o) {
    double base;
    int exp;
    base = b + o.b;
    exp = e + o.e;

    Power temp(base, exp);
    return temp;
  }
  operator double() { return val; } // convert to double
};

int main() {
  Power x(4.0, 2);
  double a;

  a = x;             // convert to double
  cout << x + 1.2; // convert x to double and add 100.2
  cout << "\n";

  Power y(3.3, 3), z(0, 0);

  z = x + y;  // no conversion
  a = z;      // convert to double
  cout << a;

  return 0;
}

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