Rules for design of C + + functions

1. If the parameter is a pointer and only for input purposes, you should add a const before the type to prevent the pointer from being modified outside the function body.
2. If the input parameter passes the object as a value, it should be passed in const& mode, which saves the construction and destruction of the temporary object.
3. The normal value is obtained by the output parameter, and the error ID is returned with the return statement.
4. Parameter defaults can only appear in the definition of a function, and can only be defaulted from back to front
5. Inline functions must be placed in the function definition.

Rules for design of C + + functions