DEFINITION MODULE Shuffle;

(*
 These routines are for randomly picking numbers from a sequential list
 so that no number is picked more than once.
 Applications are card shuffling type operations where a set of objects
 need to be rearranged/picked randomly.

 First call Create to build a list with the specified range, then use Next
 to get numbers within that range, randomly without repeating a number.
 Call Reset to reset the list to have all 'size' numbers available again.
 If Next is called more than 'size' times, a Reset will be forced.
*)

(* V1.1, John Andrea, Jun.22/93 -add Copy and Duplicate *)
(* V1.0, John Andrea, Apr.5/92 *)
(* This code may be freely used and distributed, it may not be sold *)

EXPORT QUALIFIED Deck, Create, Reset, Next;

TYPE
    Deck;   (* opaque *)

PROCEDURE Create( VAR d :Deck; min, max :CARDINAL );

PROCEDURE Reset( d :Deck );

PROCEDURE Next( d :Deck ) :CARDINAL;

PROCEDURE Copy( d, e :Deck );
(* copy the settings of 'd' into 'e', iff min and max are the same *)

PROCEDURE Duplicate( d :Deck; VAR e :Deck );
(* make a new duplicate of 'd' in new 'e' *)

END Shuffle.