Overloaded operators: class member functions or friend functions

Class member functions:

BOOL operator = = (Const point &a) const
{
return x==a.x;
}

Friend function:

friend bool operator = = (Const point &a,const point &b)
{
return a.x==b.x;
}

Comparison of two overloaded methods:

(1) monocular operators, =, (), [], use class member functions, other binocular operators using friend functions

(2) Type conversion functions can only be defined as class member functions

(3) An operation modifies a class member to use a class member function

(4) An implicit type conversion makes it necessary to use a friend function

(5) The operator needs to be commutative when the function of the UF element

(6) Two parameters need to limit the const when the function of the UF element

Overloaded operators: class member functions or friend functions