Alternative Numerical Input

Here is the full text of our alternative numerical input example. Here, we allow the student to type in his/her answers in `standard' format. Of course, one should realize that some students, especially young ones, will be unfamiliar with the floating point notation such as
4.07e-6
so perhaps a discussion (or help screen) explaining this floating notation scheme is in order.

Non the less, here is the free form numerical alternative input example.

#!/usr/local/bin/perl -- -*- C -*-
use CGI;
$query = new CGI;
$quest = 3.4;
$debug = "true";
print $query->header;
print $query->start_html("q2.pl, Numerical Input Example");
print $query->start_form;

print <<EOF;
<P> How many feet are there in $quest miles?
EOF

$ans = 5280*$quest;

print $query->textfield('stu_ans','',10,30);
print "<P> Is the above answer correct?",$query->submit("Send Answer in For Grading");
print $query->reset;
print $query->end_form;


$returned_ans = $query->param('stu_ans');
if ( $query->param('stu_ans') ne '') {
	print "<em>Student_answer, </em>$returned_ans";
	$returned_ans =~ s/\//gi; 
	$returned_ans =~ s/\$//gi; 
	$returned_ans =~ s/#//gi; 
	$returned_ans =~ s/~//gi;
	$stu_ans = eval($returned_ans);



$criterion = ($stu_ans - $ans)**2;
if($debug eq "true"){
	print "<br>Actual answer recorded in question = ",$ans;
	print "<br> Criterion for acceptance = ",$criterion;
	}

print "<br> student answer = ",$returned_ans;
	if ( (($stu_ans - $ans)**2  ) ge 0.01 ) 
		{print "<em>, was WRONG!</EM>
		<IMG SRC=../icons/checkno.gif>"}
		 else {print "<em>, was RIGHT! </EM>
		<IMG SRC=../icons/check.gif>"};
};
print $query->end_html;

Click Here to see this Alternative Numerical Input Example.

Some random comments:

It is a good idea to use the debug flag the way we do, so that setting to false keeps the debugging information available in case the question is itself questioned.
To prevent hackers from entering our system, we remove backslashes, dollar signs, pound signs, and tildes from the student responses before we allow them to be processed in any way.
```
	$returned_ans =~ s/\//gi; 
	$returned_ans =~ s/\$//gi; 
	$returned_ans =~ s/#//gi; 
	$returned_ans =~ s/~//gi;
	$stu_ans = eval($returned_ans);
```

Other than that, everything else is standard.