How to make Dot function in c++?

Question

I see things like
str.replace(5,2,”hi”);

But I don’t understand how the function was made if it’s not a class? Anyone know how?

Answer 1

https://www.w3schools.com/cpp/cpp_class_methods.asp

Answer 2

If a function is not a member of a class or struct, then you can invoke it directly by its name (and arguments - as necessary) without any need of the "dot".

The "dot" is also known as member access operator

https://en.cppreference.com/w/cpp/language/operator_precedence