public String explain(){
  StringBuffer sb=new StringBuffer();
  sb.append("I don't understand your formula ");
  quotify(sb,scanner.getInput());
  sb.append(".\n\n");
  explainWhere(sb);
  explainWhy(sb);
  explainWhat(sb);
  return sb.toString();
}

public String explain ( ) { StringBuffer sb = new StringBuffer ( ) ; sb . append ( "I don't understand your formula " ) ; quotify ( sb , scanner . getInput ( ) ) ; sb . append ( ".\n\n" ) ; explainWhere ( sb ) ; explainWhy ( sb ) ; explainWhat ( sb ) ; return sb . toString ( ) ; }
give a long , hopefully helpful error message .
