-- This example has three compilation units :
--   The generic package specification for GENSUMPKG
--   The package body for GENSUMPKG
--   The test procedure that instantiates GENSUMPKG with
--       generic actual parameters  INTEGER and MY_ARRAY

generic                                                 -- gensumpkg.ads
  type ELEMENT is private ;
  type KEY_1 is array ( INTEGER range <> ) of ELEMENT ;
  with function "+" ( U , V : ELEMENT ) return ELEMENT is <> ;
package GENSUMPKG is
  procedure SUM ( A : in out KEY_1 ) ;
end GENSUMPKG ;      -- end of first compilation unit


package body GENSUMPKG is                              -- gensumpkg.adb
  procedure SUM ( A : in out KEY_1 ) is
    TOTAL : ELEMENT := A ( A'FIRST ) ; -- no numbers allowed
  begin
    for I in A'FIRST + 1 .. A'LAST loop
      TOTAL := TOTAL + A ( I ) ;
    end loop ;
    A ( A'FIRST ) := TOTAL ;
  end SUM ;
end GENSUMPKG ; -- end of second compilation unit


with TEXT_IO ; use TEXT_IO ;                          -- testgens.adb
with GENSUMPKG ;
procedure TEST_GENSUMPKG is
  type MY_ARRAY is array ( INTEGER range <> ) of INTEGER ;
  STUFF : MY_ARRAY ( 1 .. 3 ) := ( 1 , 2 , 3 ) ;

  package INT_IO is new INTEGER_IO ( INTEGER ) ;
  use INT_IO ;

  -- This is the generic instantiation of the package above

  package MY_SUM is new GENSUMPKG ( ELEMENT => INTEGER , KEY_1 => MY_ARRAY );

  --or   package MY_SUM is new GENSUMPKG ( INTEGER , MY_ARRAY ) ; -- positional

  use MY_SUM ; -- optional, could also write MY_SUM.SUM below

begin
  PUT_LINE ( " GENERIC SUM PACKAGE " ) ;
  SUM ( STUFF ) ; --                   call procedure in instantiated package
  PUT ( STUFF( 1 )) ;
  PUT_LINE ( " = SUM " ) ;
end TEST_GENSUMPKG ;

-- GENERIC SUM PACKAGE              \___results of running.
--          6 = SUM                 /