Fundamental Theorem of Calculus: handling the preview button.

When clicking the preview button, messages that you prepare for the student will be displayed. In the problem below you learn how to prevent this.

# Created by Nikola Kuzmanovski

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

DOCUMENT();      

loadMacros(
   "PGstandard.pl",
   "MathObjects.pl",
   "PGinfo.pl",   
);

TEXT(beginproblem());
$showPartialCorrectAnswers = 1;

##############################################################
#
#  Setup
#
#


Context("Numeric");
$f_DownLim = random(-9, 9, 1);
$f_UpLim = random($f_DownLim + 5, $f_DownLim + 15, 1);

$integral = random(-9, 9, 1) + 1;
$F_UpLim = random(-9, 9, 1) + 1;

$F_DownLim = $F_UpLim - $integral;
##############################################################
#
#  Text
#
#

Context()->texStrings;
BEGIN_TEXT
Suppose that you have two functions \(f(x)\) and \(F(x)\) such that \(F'(x)=f(x)\).
Also, suppose that
\begin{eqnarray*}
\int_{$f_DownLim}^{$f_UpLim} f(x) &=& $integral\\
F($f_UpLim) &=& $F_UpLim.
\end{eqnarray*}

Then \(F($f_DownLim) = \) \{ans_rule\}.
END_TEXT
Context()->normalStrings;

##############################################################
#
#  Answers
#
#

$checkFTCSolve = sub{
	if($inputs_ref->{previewAnswers}){
		return 0.0;
	}
	
	my ($correctAns, $studentAns, $ansHash) = @_;
	$score = 0.0;
	
	if($correctAns == $studentAns){
		$ansHash->{ans_message} = "Great Job!";
		$score = 1.0;
	}elsif(Real("$F_UpLim + $integral") == $studentAns){
		$ansHash->{ans_message} = "You might have made a mistake when moving the integral to the other side of the equation. It could also be that you made a mistake when negating the equation.";
		$score = 0.9;
	}elsif(Real("-$F_UpLim - $integral") == $studentAns){
		$ansHash->{ans_message} = "You might have made a mistake when moving F(".$f_UpLim.") to the other side of the equation. It could also be that you made a mistake when negating the equation.";
		$score = 0.9;
	}elsif(Real("-$F_UpLim + $integral") == $studentAns){
		$ansHash->{ans_message} = "You made several algebra mistakes. Go back and check you work. Make sure you are careful when moving things around the = and when negating.";
		$score = 0.8;
	}else{
		$ansHash->{ans_message} = "Sorry, you didn't get any credit. Try reviewing the material on the Fundamental Theorem of Calculus.";
		$score = 0.0;
	}
	
	return $score;
};

ANS(Real("$F_DownLim")->cmp(checker => $checkFTCSolve));

ENDDOCUMENT();        

Exercises:

1. Remove the "PGinfo.pl", line. What happens?
2. Remove the first if statement in the answer checker. What happens?