Issues with attention to C + + operator overloading

C++primer Fourth Edition 435

1. Assignment (=), subscript ([]), Call (()), member Access Arrow (-) operator must be defined as member, when defined as non-member, compiler error

2. Like assignment, a conforming assignment operator should normally be defined as a member of a class, but no compilation error occurs when a compound assignment operator is defined as a non-member

3. Some other operators, such as self-increment, self-subtract, and dereference, that change the state of an object or a given type, should normally be defined as members of a class

4. Symmetric operations, such as arithmetic operators, equality operators, relational operators, and bitwise operators, are best defined as normal non-member functions

Operators that cannot be overloaded:

::       .*      . ? :

Issues with attention to C + + operator overloading