public boolean add(symbol_set other) throws internal_error {
  boolean result=false;
  not_null(other);
  for (Enumeration e=other.all(); e.hasMoreElements(); )   result=add((symbol)e.nextElement()) || result;
  return result;
}

public boolean add ( symbol_set other ) throws internal_error { boolean result = false ; not_null ( other ) ; for ( Enumeration e = other . all ( ) ; e . hasMoreElements ( ) ; ) result = add ( ( symbol ) e . nextElement ( ) ) || result ; return result ; }
add ( union ) in a complete set .
