##########################################################
#
#  Example showing how to use the built-in answer checker for parsed values.
#

DOCUMENT();        # This should be the first executable line in the problem.

loadMacros(
  "PGbasicmacros.pl",
  "PGanswermacros.pl",
  "Parser.pl",
  "parserUtils.pl",
);

TEXT(beginproblem());

##########################################################
#
#  The setup
#

Context("Numeric");

$a = random(1,5,1);
$f = Formula("(x^2-$a)/(x^2+$a)");

##########################################################
#
#  The problem text
#

Context()->texStrings;
BEGIN_TEXT

Suppose \(\displaystyle f(x) = $f\).
$PAR
Then \(f\) is defined for all \(x\) except for \{ans_rule(30)\}.
$PAR
${BCENTER}
${BSMALL}
To enter more than one value, separate them by commas.$BR
Enter ${LQ}${BTT}NONE${ETT}${RQ} if there are no such values.
${ESMALL}
${ECENTER}

END_TEXT
Context()->normalStrings;

###########################################################
#
#  The answer
#

ANS(List("NONE")->cmp);
$showPartialCorrectAnswers = 1;

###########################################################

ENDDOCUMENT();        # This should be the last executable line in the problem.