The use of const to specify function arguments and return values is another place where the concept of constants can be confusing. If you are passing objects by value, specifying const has no meaning to the client (it means that the passed argument cannot be modified inside the function). If you are returning an object of a user-defined type by value as a const, it means the returned value cannot be modified. If you are passing and returning addresses, const is a promise that the destination of the address will not be changed.