** Using WeBWorK **

Hi everyone,

We are encountering the following error in several problems where answers must be selected from a radio button or a popup menu:

----------------

PG question processing error messages

PG warning messages

Error in Translator.pm::process_answers: Answer AnSwEr0001: Unrecognized evaluator type |HASH|
Answer evaluator AnSwEr0001 was not executed due to errors.

----------------

Since upgrading our server to version 2.19, we’ve been facing several issues that were not present prior to the upgrade. We may need to rebuild the server to resolve these issues.

Below is a sample code for a problem that triggers this error. 

Thanks in advance.

DOCUMENT();

loadMacros(

  "PGgraphmacros.pl",

  "PGstandard.pl",

  "MathObjects.pl",

  "PGML.pl",

  "parserRadioButtons.pl",

  "contextFraction.pl",

  "PCCgraphMacros.pl",

  "pccTables.pl",

  "PGcourse.pl",

);

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

Context("Point");

$refreshCachedImages=1;

#These two arrays store the coordinates of the intersections.

#(x[0],y[0]) is the correct solution in the correct graph.

#(x[1],y[1]), (x[2],y[2]), (x[3],y[3]) are incorrect solutions.

#(x[4],y[4]) is used in the solution.

@x=();

@y=();

# This array stores the y-intercepts of lines.

# b[0][0] and b[0][1] are y-intercepts of lines in the correct graph.

# b[i][0] and b[i][1] are y-intercepts of lines in wrong graphs.

# b[i][2] stores whether the second line is vertical or horizontal (used

# in graph's alt and title.

# b[4][0] and b[4][1] are used in solution.

@b=([],[],[],[],[]); 

#Set the correct solution.

$x[0] = non_zero_random(-3,3,1);

do {$y[0] = non_zero_random(-3,3,1);} until ($y[0]!=$x[0]);

$intersection = Compute("($x[0],$y[0])");

Context("Fraction");

Context()->noreduce("(-x)-y","(-x)+y");

#Set both lines in the correct solution graph

do {$b[0][0]=$y[0]+non_zero_random(2,4,1)*random(-1,1,2);}

  until ($y[0] != (($y[0]-$b[0][0])/$x[0]*$y[0]+$b[0][0])); #prevents duplicate graphs

$b[0][1]=$y[0];

$b[0][2]="horizontal";

#Set wrong solutions

do {$x[1] = $x[0]+random(-1,1,2);} until ($x[1]!=0);

$y[1] = $y[0];

$b[1][0]=$b[0][0];

$b[1][1]=$b[0][1];

$b[1][2]="horizontal";

$b[2][0]=$b[0][0];

$x[2] = $y[0];

$y[2] = ($y[0]-$b[0][0])/$x[0]*$y[0] + $b[0][0];

$b[2][2]="vertical";

$b[3][0]=$b[0][0];

$x[3] = $x[0];

$y[3] = $y[0];

$b[3][2]="vertical";

#$x[4] and $y[4] are used in solution.

$x[4] = $x[0];

$y[4] = $y[0];

$b[4][0]=$b[0][0];

$b[4][1]=$b[0][1];

$b[4][2]=$b[0][2];

#Dump out the correct answer's slope's rise and run. 

#These will be used in the solution.

$m0Correct = Fraction($y[0]-$b[0][0],$x[0])->reduce;

@temp = $m0Correct->value;

$m0Rise = @temp[0];

$m0Run = @temp[1];

$m1Correct = 0;

#Create a hash and its inverse that randomizes the order of the four graphs.

%scramble = ();

%inverse = ();

for my $i (0..3) {

  do {$temp = list_random(0..3)} until !(grep(/^$temp$/,values %scramble) );

  $scramble{$i} = $temp;

  $inverse{$temp} = $i;

};

$scramble{4} = 4;

$inverse{4} = 4;

$xmin = -10;

$xmax = -$xmin;

$ymin = -10;

$ymax = -$ymin;

#These two variables decide how many labels are on each axis.

$xmark = ceil($xmax/10);

$ymark = ceil($ymax/10);

@gr=();

#$gr[0] through $gr[3] are options; $gr[4] is used in solution.

for ($i=0;$i<=4;$i++) {

   $gr[$i] = init_graph($xmin,$ymin,$xmax,$ymax,

   axes=>[0,0],

   grid=>[$xmax-$xmin,$ymax-$ymin],

   size=>[xPixels(),yPixels()]

   );

   $gr[$i]->lb('reset');

   for ($j=-$xmax+$xmark;$j<$xmax;$j=$j+$xmark) {

      $gr[$i]->lb( new Label($j,  -0.1, $j,'black','center','top'));

   }

   for ($j=-$ymax+$ymark;$j<$ymax;$j=$j+$ymark) {

      if (Real($j) == 0) {next;}

      $gr[$i]->lb( new Label(0,  $j,' '.$j,'black','left','middle'));

   }

   $gr[$i]->lb( new Label($xmin, $ymax, ' '.$ALPHABET[$inverse{$i}], 'black', 'left', 'top')) unless ($i==4);

   $m1 = ($y[$i]-$b[$i][0])/$x[$i];

   add_functions($gr[$i], "$m1*x+$b[$i][0] for x in <$xmin,$xmax> using color:red and weight:1");

   if (($i==0) || ($i==1) || ($i==4)) {

      $m2 = ($y[$i]-$b[$i][1])/$x[$i];

      add_functions($gr[$i], "$m2*x+$b[$i][1] for x in <$xmin,$xmax> using color:blue and weight:1");

   }

   if ($i==2) {

      $gr[$i]->moveTo($y[0],$ymin);

      $gr[$i]->lineTo($y[0],$ymax,'blue',2);

   }

   if ($i==3) {

      $gr[$i]->moveTo($x[0],$ymin);

      $gr[$i]->lineTo($x[0],$ymax,'blue',2);

   }

   $ALTtags[$i]="Graph $ALPHABET[$inverse{$i}]: This is a graph of two lines intersecting at ($x[$i],$y[$i]). One line is $b[$i][2].";

}

pop(@ALTtags);

push(@ALTtags,"This is a graph of two lines intersecting at ($x[4],$y[4]). One line is $b[4][2].");

$radio = RadioButtons(

  ["A","B","C","D"],

  $ALPHABET[$inverse{0}], # correct answer

  order => ["A","B","C","D"],

);

#for display purposes

$func0 = Compute("$m0Correct*x+ $b[0][0]")->reduce;

$horiY = $y[0];

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

TEXT(beginproblem());

BEGIN_PGML

Solve the system of equations by graphing. Choose the graph that represents the two given line equations, and then enter the solution. 

    [``

  \left\{\begin{aligned}

  y &=  [$func0] \\

  y &=  [$horiY] \\

\end{aligned}

  \right.

    ``]

[@EnlargeImageStatementPGML()@]** 

    The correct graph is graph    

    [@$radio->buttons()@]*

The solution of this system, written as an ordered pair, is [_______________].

END_PGML

Context()->texStrings;

BEGIN_TEXT

$PAR

$BCENTER

\{ 

LayoutTable([[image( insertGraph($gr[$scramble{0}]), width=>xScreen(), height=>yScreen(), tex_size=>TeXscalar(), extra_html_tags=>'alt = "$ALTtags[$scramble{0}]" title = "$ALTtags[$scramble{0}]"'  ),

image( insertGraph($gr[$scramble{1}]), width=>xScreen(), height=>yScreen(), tex_size=>TeXscalar(), extra_html_tags=>'alt = "$ALTtags[$scramble{1}]" title = "$ALTtags[$scramble{1}]"'  ),

],

[image( insertGraph($gr[$scramble{2}]), width=>xScreen(), height=>yScreen(), tex_size=>TeXscalar(), extra_html_tags=>'alt = "$ALTtags[$scramble{2}]" title = "$ALTtags[$scramble{2}]"'  ),

image( insertGraph($gr[$scramble{3}]), width=>xScreen(), height=>yScreen(), tex_size=>TeXscalar(), extra_html_tags=>'alt = "$ALTtags[$scramble{3}]" title = "$ALTtags[$scramble{3}]"'  )

]], allcellcss => "padding:20pt;")

\}

$ECENTER

$PAR

END_TEXT

Context()->normalStrings;

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

ANS( $radio->cmp() );

ANS( $intersection->cmp() );

#Graph the intersection in solution.

$gr[4]->stamps( closed_circle($x[0],$y[0],'black') );

$gr[4]->lb( new Label($x[0],$y[0]," ($x[0],$y[0])",'black','left','top'));

#Graph slope triangle in the first line.

$gr[4]->moveTo(0,$b[0][0]);

$xCor=0;

$yCor=$b[0][0];

$xStep = $x[0]>0 ? $m0Run : -$m0Run;

$yStep = ($y[0]-$yCor)>0 ? abs($m0Rise) : -abs($m0Rise);

do {

   $xCor += $xStep;

   $gr[4]->lineTo($xCor,$yCor,'red',2);

   $yCor += $yStep;

   $gr[4]->lineTo($xCor,$yCor,'red',2);

} until ($xCor==$x[0]);

Context()->texStrings;

BEGIN_SOLUTION

$PAR

To solve a system of linear equations by graphing, one way is to first graph each line's \(y\)-intercept, and then draw slope triangles until we find the intersection. If we use a method where we connect two points using a straightedge, slight inaccuracies in the placement of the straightedge can lead to very inaccurate solutions.$PAR

For this problem, the first equation is given in slope-intercept form. We can graph its \(y\)-intercept, and then draw slope triangles. 

$PAR

The second line is horizontal.

$PAR

See solution in the graph:

$PAR

$BCENTER

\{ image( insertGraph($gr[4]), width=>xScreen(), height=>yScreen(), tex_size=>TeXscalar(), extra_html_tags=>'alt = "$ALTtags[$scramble{4}]" title = "$ALTtags[$scramble{4}]"'  ) \}

$ECENTER

$PAR

The solution to this system of equations is \( ($x[0],$y[0]) \). \{ $radio->correct_ans() \} is the correct answer.

$PAR

END_SOLUTION

Context()->normalStrings;

ENDDOCUMENT();