PRB: C2666 Error Generated with Overloaded Operator

RESOLUTION

1. Typecast the operand that is causing the ambiguity. For example:

         c = 1234L + a;
   						

   -or-

         c = (long)1234 + a;
   						

2. Remove the float operator from the Fraction class. This prevents a default operator "+" from being provided by the compiler because there is no conversion provided by the user for the second argument. The selection is made from the list of three user-provided "+" operators. For the first argument, the first operator

         + ( long,          const Fraction& )
   						

   is chosen because a trivial conversion is required for int to long. The same selection is also made for the second argument, making the operator

         + ( long,           const Fraction& )
   						

   common to both the selections, and thus resolving the ambiguity.

Sample Code

/* Compile Options needed: none
*/ 

class Fraction {
 private:
   int x;
   int y;
 public:
   Fraction(int a=0, int b=0) : x(a), y(b) { }
   ~Fraction(){}
   operator float () {return int(x);}
};

Fraction& operator+(long i, const Fraction& ) { Fraction f ; return f; }
Fraction& operator+(const  Fraction& , const Fraction& ){ Fraction f;
return f; }
Fraction& operator+(const Fraction&  , long i ) { Fraction f ; return f;}

void main()
{
   Fraction a(2,3), c;

   c =     1234 + a;   // error C2666: '+' : 4 overloads have
              // similar conversion
}