INTERFACE ObCommand;
IMPORT ObErr;

TYPE
  T =
    BRANDED OBJECT
      name: TEXT;
      sortingName: TEXT;
      Exec: Proc;
    END;

  Set <: ROOT;

  Proc =
    PROCEDURE(self: T; arg: TEXT:=NIL; data: REFANY:=NIL) RAISES {ObErr.Fail};
      (* When arg is "!", the command should give a one-line description
         of itself. If arg is "?", the command should give a full
         description. Otherwise, arg can be parsed to set options. *)

PROCEDURE Setup();

PROCEDURE NewSet(): Set;

PROCEDURE Register(set: Set; command: T);
PROCEDURE ReRegister(set: Set; name: TEXT; proc: Proc);

PROCEDURE Exec(name: TEXT; arg: TEXT:=NIL; set: Set; data: REFANY:=NIL)
  RAISES {ObErr.Fail};

When name=? all the register commands are invoked with argument !. Otherwise, the named command, if found, is invoked with argument arg. Data is passed along to the commands.

END ObCommand.