C++ Unary - Operator Overload Won't Compile -

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i attempting create overloaded unary - operator can't code compile. cut-down version of code follows:-

class frag {     public:          frag myfunc  (frag oper1,                       frag oper2);         frag myfunc2  (frag oper1,                       frag oper2);          friend frag operator + (frag &oper1,                                 frag &oper2);          frag operator - ()         {             frag f;             f.element = -element;             return f;         }      private:          int element;  };  frag myfunc (frag oper1, frag oper2) {     return oper1 + -oper2; }  frag myfunc2 (frag oper1, frag oper2) {     return oper1 + oper2; }  frag operator+ (frag &oper1, frag &oper2) {     frag innerfrag;     innerfrag.element = oper1.element + oper2.element;     return innerfrag; }

the compiler reports...

/home/brian/desktop/frag.hpp: in function ‘frag myfunc(frag, frag)’: /home/brian/desktop/frag.hpp:41: error: no match ‘operator+’ in ‘oper1 + oper2.frag::operator-()’ /home/brian/desktop/frag.hpp:16: note: candidates are: frag operator+(frag&, frag&)

could suggest need doing here?

const-correctness

this has be

 frag operator+ (const frag &oper1, const frag &oper2);

or else operands can't temporaries, such return value of operator-

and unary minus should rather be:

frag operator - () const;

since shouldn't modify operand.


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