UsingWW: Nandor Sieben - evaluator confusion

$inactiveTopic$ evaluator confusion

topic started 7/14/2005; 12:49:09 AM
last post 7/14/2005; 9:19:05 AM

$user$ Nandor Sieben - evaluator confusion $blueArrow$
7/14/2005; 12:49:09 AM (reads: 646, responses: 2)

The following code doesn't work. It gives the warning: not a CODE reference. I would like to write my own evaluator that calls a standard evaluator.

TEXT(&beginproblem);                    
sub ans_eval {
my $correct = shift;
my $myeval = num_cmp($correct);
sub {
 my $in = shift;
 my $ans_hash =  &$myeval($in);
# modife $ans_hash here a little
 $ans_hash;
}
}

BEGIN_TEXT
How much is 5+2?
{ ans_rule(10) }
END_TEXT

ANS( ans_eval(7) );

What is the problem with it? The following simple perl code works, and I would think the answer evaluator uses the same principle except it returns a reference to an answer hash.

#!/usr/bin/perl -w                                                                                            

sub ff {              

 my $c = shift;

sub {

my $a = shift;

$c*$a;

}

}

$reff = ff(2);

print &$reff(3);

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$user$ Nandor Sieben - Re: evaluator confusion $blueArrow$
7/14/2005; 1:42:15 AM (reads: 834, responses: 0)

I got it. Now I know that there are old style and new style evaluators. I need $myeval_evaluate($in). Where can I find info about the answer evaluator object?

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$user$ Michael Gage - Re: evaluator confusion $blueArrow$
7/14/2005; 9:19:05 AM (reads: 839, responses: 0)

The old style (for Perl 4) is described at http://webwork.math.rochester.edu/docs/docs/pglanguage/answerevaluators.html#WAEF. There is also some discussion at http://webhost.math.rochester.edu/webworkdocs/discuss/msgReader$763 about handling old and new style answer evaluators. I encourage you to use the AnswerEvaluator object as described in AnswerHash.pm. You may need to look at the code itself. For modifying existing answer evaluators, which is a lot of what you are trying to do at the moment, take a look at the code in PGasu.pl. John Jones has a number of straightforeward examples of modifying existing answer evaluators.

Hope this helps.

-- Mike

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