What is friend function ?

Question

friend function explanation

Answer 1

it's a function that's not a class member but is treated like one

Answer 2

https://www.tutorialspoint.com/cplusplus/cpp_friend_functions.htm

https://www.programiz.com/cpp-programming/friend-function-class

http://en.cppreference.com/w/cpp/language/friend

https://www.w3schools.in/cplusplus-tutorial/friend-function/