However, I ran into the issue of the call to Multianswer doesn't even get to my custom checker because it is checking to see if the the answer has any error messages before doing so. I am providing the 3x3 identity matrix and a List of two numbers to Multianswer and so if the student enters anything but a 3x3 matrix, it gives the "Matrix dimension is not correct" error (even if I add the showDimensionHints => 0) and does not go to my custom checker. FYI, I know this is occurring in the entry_check and perform_check subroutines of the parserMultianswer.pl macro, but I don't know how to make them look past the dimensions of the matrix. My attempts at editing the file only lead to problems.

Any ideas how how I can do what I want? Thanks in advance! Here is the code I'm trying to use that isn't working:

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

# initialization

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

DOCUMENT();

loadMacros(

"MathObjects.pl",

"PGstandard.pl",

"PGmatrixmacros.pl",

"parserMultiAnswer.pl",

);

TEXT(beginproblem());

$showPartialCorrectAnswers = 0;

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

# setup contexts and variables

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

Context("Matrix");

Context()->strings->add(true=>{}, false=>{}, t=>{alias=>"true"}, f=>{alias=>"false"});

sub getCofacMat {

my ($a, $b, $A) = @_;

my @d = $A->dimensions;

return if ($a < 0 || $b < 0 || $a > $d[0] || $b > $d[1]);

my $M = new MatrixReal1($d[0]-1,$d[1]-1);

my $m = 0; my $n = 0;

for ($i = 0; $i < $d[0]; $i++) {

for ($j = 0; $j < $d[1]; $j++) {

if ($i != $a - 1 && $j != $b - 1) {

$M->assign($m+1,$n+1,$A->element($i+1,$j+1));

$n++;

if ($n == $d[1] - 1) {$m++; $n = 0};

}

}

}

$M = Matrix($M);

return $M;

}

$answer = MultiAnswer(Value::Matrix->I(3), List(3,1))->with(

singleResult => 0,

allowBlankAnswers => 1,

showDimensionHints => 0,

checkTypes => 0,

checker => sub {

my ($correct, $student, $self) = @_;

my ($c1, $c2) = @{$correct};

my ($s1, $s2) = @{$student};

return [0,0] if (!Value::classMatch($s1, 'Matrix') || !Value::classMatch($s2, 'List'));

return [0,0] unless $s1->isSquare;

@a = $s1->dimensions;

@d = @{$s2->data};

return [0,0] if (scalar(@d) != 2);

return [0,0] if (!Value::classMatch($d[0], 'Real') && !Value::classMatch($d[1], 'Real'));

return [0,0] if (floor($d[0]) != $d[0] || floor($d[1]) != $d[1]);

return [0,0] if ($d[0] < 1 || $d[0] > $a[0] || $d[1] < 1 || $d[1] > $a[0]);

$diag1 = 1; $diag2 = 0;

for ($i = 0; $i < $a[0]; $i++) {

for ($j = 0; $j < $a[0]; $j++) {

if ($i != $j && $s1->element($i+1,$j+1) != 0) { $diag1= 0 };

}

}

my $B = getCofacMat($d[0], $d[1], $s1);

for ($i = 0; $i < $a[0]-1; $i++) {

for ($j = 0; $j < $a[0]-1; $j++) {

if ($i != $j && $B->element($i+1,$j+1) != 0) { $diag2 = 1 };

}

}

return [1,1] if ($diag1 && $diag2);

return [0,0];

}

);

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

# state the problem

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

Context()->texStrings;

BEGIN_TEXT

Determine if the following statement is true or false:

$PAR

$SPACE $SPACE $SPACE If \(A\) is a diagonal matrix, then \(M_{ij}\) is also diagonal for all \(i\) and \(j\).

$PAR

If the answer is true, then type ${BBOLD}true${EBOLD}. If the answer is false, give an example in the first blank of a matrix in which the condition fails and type in the second blank \(i,j\) if \(M_{ij}\) is not diagonal. For example, type 1, 2 (separate with commas) for \(M_{12}\). $PAR

Answer: \{ $answer->ans_rule(35) \} \{ $answer->ans_rule(8) \}

$PAR

${BBOLD}Help:${EBOLD} To enter a matrix use $BBOLD [[ ],[ ]] $EBOLD. For example, to enter the \(3\times 3\) matrix

$PAR\[

\left[\begin{array}{rrr}

1 & 1 & 2 \\ 2 & 3 & 5 \\ 1 & -1 & 5

\end{array}\right]

\]$PAR you would type [[1,1,2],[2,3,5],[1,-1,5]], so each inside set of [ ] represents a row.

END_TEXT

Context()->normalStrings;

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

# check the answer

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

ANS($answer->cmp());