WeBWorK Problems

Answer up to multiplication by a nonzero constant and added variables

Answer up to multiplication by a nonzero constant and added variables

by David Protas -
Number of replies: 2
Is it possible to have an answer with an added variable checked up to a nonzero parameter multiple? I have an ODE with solutions given implicitly by F(x,y) = C. I want students to enter F(x,y). I have written the answer (in old style code, which I plan to update) as
         ANS(fun_cmp("k($ans) + c", var=>['x','y'], params=>['k','c'] ) );
The trouble is that 0 is counted as a correct answer. Can anyone help?
In reply to David Protas

Re: Answer up to multiplication by a nonzero constant and added variables

by Gavin LaRose -
Hi David,

Maybe something like the following? 

  Context("Numeric")->variables->are(
    x=>'Real', y=>'Real' );

  $ans = "...";
  $ansObj = Compute( $ans );
  ...
  ANS( $ansObj->cmp( checker=> sub {
    my ( $correct, $student, $self ) = @_;
    my $context = Context()->copy;
    $context->flags->set(no_parameters=>0);
    $context->variables->add(
      c=>'Parameter', k=>'Parameter' );

    my $c = Formula($context,'c');
    my $k = Formula($context,'k');

    $student = Formula($context,$student);
    $correct = Formula($context,"$k*($ans) + $c");
    return $correct == $student &&
        Compute(0) != $student;
}));

(This is shamelessly copied from the techniques page on adaptive parameters: <http://http://webwork.maa.org/wiki/AdaptiveParameters>.)

Gavin

In reply to Gavin LaRose

Re: Answer up to multiplication by a nonzero constant and added variables

by David Protas -
Gavin,

Thanks. It works like a charm.

David