"binary 'operator ' has too many parameters-CodePudding

Trying to implement operator overloading using the following code:

class Number
{
    T value;
public:
    Number(T v);
    Number();
    Number<T> operator  (Number<T>&, const Number<T> &);
    T getValue() { return value; };
};


template <typename T>
Number<T>::Number(T val):value(val) { }

template <typename T> 
Number<T> Number<T>::operator  (Number<T>& lhs, const Number<T> & rhs)  {    
     return lhs.value   rhs.value;
}

Trying to emulate similar examples found online, but this attempt generates several compiler errors

'{' missing function header (old-style format list?)
binary 'operator ' has too many parameters
class template "Number" has no member "operator "

Number<T> Number<T>::operator (Number<T>& lhs, const Number<T> & rhs)

With all the decisions: whether or not to include "<T>"; whether or not to use references for sends and returns; whether or not to use "const" and/or "friend"; and whether or not to use "this", "new" and/or "->"; it's confusing enough to search for outside help :).

Any idea what (many things) I'm doing wrong?

Thanks for your consideration

CodePudding user response：

You're forgetting about the implicit this parameter that are present as the first parameter in a non-static member function.

To solve your probelm just remove the extra first parameter from operator as shown below:

template<typename T>
class Number
{
    T value;
public:
    Number(T v);
    Number();
    Number<T> operator  (const Number<T> &);//REMOVED UNNECESSARY PARAMETER
    T getValue() { return value; };
};



template <typename T>
Number<T>::Number(T val):value(val) { }

template <typename T> 
Number<T> Number<T>::operator  (const Number<T> & rhs)  {  //REMOVED UNNECESSARY PARAMETER  
     return value   rhs.value;//CHANGED lhs.value to value
}

The output of the program can be seen here.

CodePudding user response：

Remove this line:

Number<T> operator  (Number<T>&, const Number<T> &);

and define operator out of the class body this way:

template<typename T>
Number<T> operator (Number<T> const& lhs, Number<T> const& rhs) {
    auto ret{ lhs };
    ret.value  = rhs.value;
    return ret;
}