-- combinations.ads

-- n is for n things     n! / ((n-m)! m!) combinations
-- m is for m at a time
-- Vn must be the n items, unchanged by combinations
-- Vm must be of size m items, the returned combination each call
-- First must be true the first call, then set to false internally
-- Last is false if more combinations to come.
-- Last is True for the final combination

-- instantiate package:
-- package my_comb is new combinations(10, integer, integer_vector);
-- then
--   last := false;
--   first := true;
--   while not last loop
--     my_comb.comb(N, M, Vn, Vm, first, last);
--     -- use Vm combination
--   end loop;

generic
  Max_Size : integer; -- user max size
  type Item is private ; -- user item type
  type Vector_Type is array(integer range <>) of Item; -- user vector type
package Combinations is
  type Comb_Type is array(Integer range <>) of Integer;
  C : Comb_Type(0..Max_Size+1);
  Pos : Integer;
  Var : Integer;
  Mov : Integer;
  procedure Comb(N : Integer; M: Integer; Vn : in Vector_Type;
                 Vm : in out Vector_Type; First : in out Boolean;
                 Last : in out Boolean);
end combinations;