-- Package to demonstrate Private Types.
    
    WITH TEXT_IO ; USE TEXT_IO ; -- make text I/O available

    PACKAGE id_handler IS

-- Package Types :

    TYPE id_number IS PRIVATE ;

-- Package Functions :

-- new_id => Genarate an id_number.
    FUNCTION new_id RETURN id_number ;

-- Package Procedures :

-- put => Output an id_number to the terminal.
    PROCEDURE put ( id : id_number ) ;

    PRIVATE -- hidden part

-- Private Type Declarations :

    TYPE id_number IS ARRAY ( 1..3 ) OF INTEGER ;

    END id_handler ; ---------------------------------------------------

    PACKAGE BODY id_handler IS

-- Local Variables :

    next_id : id_number := ( 0, 0, 0 ) ; -- zeros initially

-- Generic Package Instantiations :

    PACKAGE int_io IS NEW INTEGER_IO ( INTEGER ) ; USE int_io ;

-- Package Functions :

-- new_id => Generate a value of type id_number.
    FUNCTION new_id RETURN id_number IS

-- Local Variables :

    result : id_number ; -- local storage for result

    BEGIN -- new_id

-- copy next available id into result & update next available id
    result := next_id ;
    IF next_id ( 3 ) = 9 THEN
       next_id ( 3 ) := 0 ;
       IF next_id ( 2 ) = 9 THEN
          next_id ( 2 ) := 0 ;
          IF next_id ( 1 ) = 9 THEN
             next_id ( 1 ) := 0 ;
          ELSE
             next_id ( 1 ) := next_id ( 1 ) + 1 ;
          END IF ;
       ELSE
          next_id ( 2 ) := next_id ( 2 ) + 1 ;
       END IF ;
    ELSE
       next_id ( 3 ) := next_id ( 3 ) + 1 ;
    END IF ;
    RETURN result ;

    END new_id ; -------------------------------------------------------

-- Package Procedures :

-- put => Write out value of type id_number.
    PROCEDURE put ( id : id_number ) IS

    BEGIN -- put

-- uses int_io put
    PUT ( id ( 1 ), 1 ) ; PUT ( "-" ) ; PUT ( id ( 2 ), 1 ) ;
    PUT ( "-" ) ; PUT ( id ( 3 ), 1 ) ;

    END put ; ----------------------------------------------------------

    END id_handler ; ---------------------------------------------------