-- package for construction and manipulation of integer lists

-- authors: Rob Irving, Lorna Love
-- final version: 17 January 2001

package Integer_List_Package is

  type Integer_List_Type is private;

  procedure Create_Empty_List( L : out Integer_List_Type );
  -- creates the empty list L

  function Is_Empty ( L : Integer_List_Type ) return Boolean;
  -- returns True if list L is empty, and False otherwise

  procedure Insert ( I : in Integer; L : in out Integer_List_Type );
  -- adds the integer I to the rear of list L
  -- assumes I is not already present in L

  procedure Remove ( I : in Integer; L : in out Integer_List_Type );
  -- removes the integer I, if it exists, from the list L
  -- assumes I is present at most once in L

  procedure Print_List ( L : in Integer_List_Type);
  -- prints the contents of the list L to standard output
  
  function List_Length(L : in Integer_List_Type) return Natural;
  -- returns the length of the list L

private

  type Node_Type;
  type Node_Access is access Node_Type;

  type Node_Type is
    record
      Int : Integer;
      Next : Node_Access;
  end record;

  type Integer_List_Type is
    record
      First, Last : Node_Access;
    end record;

end Integer_List_Package;