##########################################################
#
#  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("Interval");

$a = non_zero_random(-5,5,1);
$f = Formula("(x^2+1)/(x-$a)")->reduce;
$R = Union("(-inf,$a) U ($a,inf)");

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

Context()->texStrings;
BEGIN_TEXT

Suppose \(\displaystyle f(x) = $f\).
$PAR
Then \(f\) is defined on the region \{ans_rule(30)\}.
$PAR
${BCENTER}
${BSMALL}
Several intervals can be combined using the
set union symbol, ${LQ}${BTT}U${ETT}${RQ}.$BR
Use ${LQ}${BTT}infinity${ETT}${RQ} for ${LQ}\(\infty\)${RQ} and
${LQ}${BTT}-infinity${ETT}${RQ} for ${LQ}\(-\infty\)${RQ}.
${ESMALL}
${ECENTER}

END_TEXT
Context()->normalStrings;

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

ANS($R->cmp);
$showPartialCorrectAnswers=1;

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

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