class virtual person name surname gender =
object
    val mutable name = (name: string)
    val mutable surname = (surname: string)
    val mutable gender = (gender: char)
    method virtual printNameSurname : unit
    method virtual changeSurname: string -> unit
end;;

class male name surname =
object
    inherit person name surname 'm'
    method printNameSurname = Printf.printf "name %s surname %s gender %c" name surname gender
    method changeSurname newSurname = surname <- newSurname
end;;

class female name surname =
object
    inherit person name surname 'f'
    method printNameSurname = Printf.printf "name %s surname %s gender %c" name surname gender
    method changeSurname newSurname = surname <- newSurname
end;;

class child name surname gender =
object
    inherit person name surname gender
    method printNameSurname = Printf.printf "name %s surname %s gender %c" name surname gender
    method changeSurname newSurname = surname <- newSurname
end;;


class family familyName husband wife =
object
    (*here i want the wife to take the surname of the husband*)
end;;