Member Function vs. Non-Member Function for Operator Overloading: Which is Better?

Operator Overloading: Member Function vs. Non-Member Function

When overloading an operator, developers may choose to implement it as a member or non-member function. While member functions offer simplicity for the first operand being a class object, they face limitations when the first operand is not a class.

The asymmetry of member function-overloaded operators, with the first parameter being the implicit this pointer, poses a problem when the first operand is not of the same class type. For instance, the expression 10.0 s2 cannot be evaluated using a member function overload.

Non-member function overloads, however, allow for symmetric comparisons, as they receive both operands as arguments. This flexibility resolves the asymmetry issue and enables operations with different types. Non-member functions also promote better encapsulation, as they do not have access to private members unless explicitly declared as friends.

In the STL algorithms, symmetric overloads are preferred due to their flexibility and ease of comparison. It is generally recommended to make non-member functions friend only if private members need to be accessed.

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