Custom Answer Checker

Setup

To set up the custom answer checker we will override the answer checker routine for the MathObject that we’re using to check the answer. Thus our answer object should be of the same type (e.g., Real, Formula, etc.) as what we want the student to be entering. For example, here we’re going to ask for a value of x such that cos(x) = cos($ans). Thus we set up the answer to be a real number.

The $ans object overrides the checker part of the MathObject. This is a subroutine which checks that the cosine of the student answer equals the cosine of the correct answer. This also values like pi/3, -pi/3 or pi/3 + 2pi to be considered correct.

We can set an error message in the answer checker by using Value->Error(“message”). This will set the message that is displayed to the student and exit the checker with an incorrect return value. For example:

 $ans = Compute('pi/3')->cmp(
     checker => sub {
         my ($correct, $student, $ansHash) = @_;
         Value->Error("Try again") if cos($student) == sqrt(3) / 2;
         return cos($correct) == cos($student);
     }
 );

Another handle tip for troubleshooting. To see all of the keys and values in the $ansHash when the submit answers button is pressed, include this in your custom answer checker:

foreach my $key ( keys %{$ansHash} ) {
  warn "key: $key, value: $ansHash->{$key}";
}