procedure nil_sub_trees(ptr : item_ptr);

var index : integer;

begin
    ptr^.sub_items := nil;
end;


procedure find_empty_sub_item(curr_item : item_ptr;
                              var return_ptr : item_ptr);

var ptr,hold : item_ptr;

begin
    ptr := curr_item^.sub_items;
    if ptr = nil then
        return_ptr := nil
    else
        begin
            repeat
                hold := ptr;
                ptr := ptr^.adj_item;
            until ptr = nil;
            return_ptr := hold;
        end;
end;