** Using WeBWorK **

Below is some parred down code which will function on WeBWork 1.6, but which fails under WeBWorK 1.7.

The reason it fails appears to be due to a change in num_cmp. Under WW1.6, the statement ($ans_eval1) = num_cmp(exp(2 * 1)); would produce the value "CODE(0x8967770)" for $ans_eval1 Under WW 1.7, the same statement produces "AnswerEvaluator=HASH(0x8a7d500)"

This explains why the code below fails. Perhaps someone can suggest a way around this difficulty. I do not know how to extract any information from this answer evaluator. I have stared at the "Answer hash datatype specification", but haven't a clue how to connect it to named answers.

Thanks in advance.

Tom Shemanske

DOCUMENT();
loadMacros(PG.pl,
PGbasicmacros.pl,
PGchoicemacros.pl,
PGanswermacros.pl,
PGauxiliaryFunctions.pl,
           );

TEXT(beginproblem());

BEGIN_TEXT
$BR
Enter the functions ( e^{2t} ) and (e^{3t}) in the blanks below

$BR

(f_1(t) = ) {NAMED_ANS_RULE(first_fcn,25)}
and (f_2(t) = ) {NAMED_ANS_RULE(second_fcn,25)}

$PAR
END_TEXT

## Grab the first answer entered by student
$firstAnswer = $inputs_ref->{first_fcn};

## An alternate means of grabbing the function
#$firstAnswer = ${$main::inputs_ref}{first_fcn} if defined(${$main::inputs_ref}{first_fcn});

## Make sure it is defined
$firstAnswer = '' unless defined($firstAnswer);

## Globally substitute (1) for t in $firstAnswer
$firstAnswer =~ s/t/(1)/g;

## Answer evaluator for the first function at t = 1
($ans_eval1) = num_cmp(exp(2 * 1));

#My mucking around trying to fix things
#$rh_ans_hash = new AnswerHash;

## Check first answer against "correct" first answer
$rh_ans_hash = &$ans_eval1($firstAnswer);

## Check answers accordingly
if ( $rh_ans_hash->{score} == 1 )
{
NAMED_ANS( first_fcn, fun_cmp("exp(2*t)", vars=>['t']) );
NAMED_ANS( second_fcn, fun_cmp("exp(3*t)", vars=>['t']) );
}
else
{
NAMED_ANS( first_fcn, fun_cmp("exp(3*t)", vars=>['t']) );
NAMED_ANS( second_fcn, fun_cmp("exp(2*t)", vars=>['t']) );
}

ENDDOCUMENT();

The error one gets is "Not a CODE reference at (eval 54) line 42."

in reference to ($ans_eval1) = num_cmp(exp(2 * 1));

which makes sense since $ans_eval1 does not evaluate to CODE but to Answer_Evaluator as mentioned above.

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I think Mike answered this some time ago. Old style answer evaluators returned function pointers, new style answer evaluators return objects which are supposed to be called using the appropriate method for the object. Under 1.6, num_cmp() returned an old style evaluator while function_cmp() returned a new style evaluator. I guess under 1.7 all answer evaluators are new style.

The following code should take care of the situation:

sub calleval {
   my ($ans_evaluator,$student_answer) = @_;
   my $rh_ans_hash = "";
   if  ( ref($ans_evaluator) eq 'AnswerEvaluator' ) { # new style
            $rh_ans_hash = $ans_evaluator->evaluate($student_answer);
   } elsif (ref($ans_evaluator) eq  'CODE' )     { #old style
            $rh_ans_hash = &$ans_evaluator($student_answer);
   } else {
            warn "There is a problem using the answer evaluator";
   }
   return $rh_ans_hash;
}

.........

$rh_ans_hash = &calleval($ans_eval1,$firstAnswer);

Zig

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