private ParameterDefinition suppliedTestInit(final Form form) throws ParseException {
    // invariante: laenge childs == 3
    checkFirstAndSecond(form);

    if (form.getChild(2).getTyp() != TSExpression.SYMBOL) {
      error("symbol expected", form.getChild(2));
    }

    return new ParameterDefinition(
        form.getFunctionSymbol(), form.getChild(1), (Symbol) form.getChild(2));
  }
  private ParameterDefinition simpleInit(final Form form) throws ParseException {
    // invariante: laenge childs == 2

    checkFirstAndSecond(form);
    return new ParameterDefinition(form.getFunctionSymbol(), form.getChild(1), null);
  }