/** helper routine to clone a new production part adding a given label */
protected production_part add_lab(production_part part, string lab)
// throws internal_error
{
/* if there is no label, or this is an action, just return the original */
if (lab == null || part.is_action()) return part;
/* otherwise build a new one with the given label attached */
return new symbol_part(((symbol_part)part).the_symbol(),lab);
}
