## WeBWorK Problems

### FormulaUpToConstant won't give helpful messages

by Liping Chen -
Number of replies: 2
I have a problem with the following code:

DOCUMENT();

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

Context("Numeric")->flags->set(
reduceConstants => 0,
reduceConstantFunctions => 0,
);
Parser::Number::NoDecimals;

$fx = Formula("3 x sqrt(x - 8)");$fx->{limits} = [9,10];

$ans = FormulaUpToConstant("6/5*(x-8)^(5/2) + 16*(x-8)^(3/2)");$ans->{limits} = [9,10];

#########################################
TEXT(beginproblem());
$showPartialCorrectAnswers = 1; Context()->texStrings; BEGIN_TEXT$PAR
Evaluate the indefinite integral:
$PAR $$\displaystyle \quad\quad \int fx \, dx =$$ \{ ans_rule(40) \} END_TEXT Context()->normalStrings; ######################################### ANS($ans -> cmp(showHints => 1) -> withPostFilter(sub {
my $ans = shift;$ans->{ans_message} = "" if $ans->{ans_message} eq "This answer is equivalent to the one you just submitted."; return$ans;
}));
ENDDOCUMENT();

If I submit an answer like 6/5*(x-8)^(5/2) + 16*(x-8)^(3/2) without adding a constant C, I cannot get the helpful hint message: Your answer is not the most general solution. This is different from other anti-derivative problems, for example, if I change this line:
$ans = FormulaUpToConstant("6/5*(x-8)^(5/2) + 16*(x-8)^(3/2)"); to$ans = FormulaUpToConstant("x");
and submit an answer x, I will get a hint: Your answer is not the most general solution. Can anyone give me some help about how to fix this problem?

As a side note, I tried to fix it by adding some scripts like:
ANS( $ans->cmp() -> withPostFilter(sub { my$ans = shift;
if(($ans->{score} == 0) && (!($ans->{ans_message}))){
$stuAns =$ans->{original_student_ans};
$stuAns =~ s/(sqrt)/::/g;$stuAns =~ s/([a-zA-Z]+)/x/g;
$stuAns =~ s/::/sqrt/g;$stuAns = Formula("$stuAns")->D();$ans->{ans_message} = "Your answer is not the most general solution." if ($fx ==$stuAns);
}
$ans->{ans_message} = "" if$ans->{ans_message} eq
"This answer is equivalent to the one you just submitted.";

return $ans; })); but it gives me some other troubles. For example, if I submit an answer like 6/5*(8-x)^(5/2) + 16*(8-x)^(3/2)+C, I will get an warning because of this line:$ans->{ans_message} = "Your answer is not the most general solution." if ($fx ==$stuAns);

Any insight on what could be going on would be really appreciated.

Thanks,
Liping

### Re: FormulaUpToConstant won't give helpful messages

by Davide Cervone -
It looks like the limits that you have assigned to $ans aren't being used at one point internally in the code that checks for whether that message is needed. Try using $ans->cmp(limits=>[9,10],showHints=>1) instead, and see if that gives you the needed message.