guideline

Use modular types rather than packed Boolean arrays when measured performance indicates.

   -- (1) Packed Boolean arrays
   --     (See ACES V2.0, test "dr_ba_bool_arrays_11")

   type Set is array (0 .. 15) of Boolean;
   pragma Pack (Set);

   S1     : Set;
   S2     : Set;
   Empty  : Set := (Set'Range => False);
   Result : Boolean;

   ...

   -- Is S1 a subset of S2?
   Result := ((S1 and not S2) = Empty);

   ---------------------------------------------------------------------

   -- (2) Modular types
   --     (See ACES V2.0, test "a9_ms_modular_oper_02")

   type Set is mod 16;

   S1     : Set;
   S2     : Set;
   Empty  : Set := 0;
   Result : Boolean;

   ...

   -- Is S1 a subset of S2?
   Result := ((S1 and not S2) = Empty);

rationale