## WeBWorK Problems

### Answer checking not working in new problem

by Hy Ginsberg -
Number of replies: 2
Hi All,

I have an integration problem where I can enter the answer exactly as it appears in the "correct " answer window, but the answer gets marked as incorrect.  I am using FormulaUpToConstant(), which I have successfully used in other problems; I have no idea what is different here.  I have removed all the extraneous pieces, and have a test problem that exhibits the trouble; here it is (I have also attached it, in case that is more convenient): -- Thanks for any help.  - Hy

DOCUMENT();

"PG.pl",
"PGbasicmacros.pl",
"PGchoicemacros.pl",
"PGauxiliaryFunctions.pl",
"parserFormulaUpToConstant.pl"
);

$showPartialCorrectAnswers = 1;$b = 16;

$ans = FormulaUpToConstant("((1/3)*(x^2-$b)^(3/2))");

TEXT(beginproblem());
BEGIN_TEXT
$BR$BR
Enter the answer: $ans$BR \{ans_rule( 60) \}
END_TEXT

ANS( $ans->cmp() ); ENDDOCUMENT(); In reply to Hy Ginsberg ### Re: Answer checking not working in new problem by Hy Ginsberg - Okay, I figured it out -- if you remove the FormulaUpToConstants() and just use the "old style" answer checker, an error arises: "Can't generate enough valid points for comparison" Changing the answer check to: ANS($ans->cmp(limits=[$a,$a+5]) );

(where $b is$a squared) fixed the problem.

But I would say that it's a bug that the error message ("Can't generate enough valid points...") gets hidden when FormulaUpToConstants() is used -- the result is that the correct answer is marked incorrect with no further information.

- Hy