## DBsubject('WeBWorK')
## DBchapter('Demos')
## DBsection('Problem')
## KEYWORDS()
## Author('Davor Cubranic')
## Institution('University of British Columbia')

DOCUMENT();
loadMacros(
"PGstandard.pl",
"MathObjects.pl",
);


### Problem setup

Context("Numeric");

$meaning_of_life = List(Real(0), Real(42));

### Displayed text

TEXT(beginproblem());
Context()->texStrings;
BEGIN_TEXT
What is the meaning of life (even if you're a nihilist)?
$PAR
\{ ans_rule(35) \}
END_TEXT
Context()->normalStrings;


### Answer and solution

ANS($meaning_of_life->cmp(list_checker => sub {
   my ($correct, $student, $ansHash) = @_;
   my $score = 0;
   my @errors; # stores error messages
   if (scalar(@{$student} == 1)) {
      my $answer = ${$student}[0];

      # iterate through correct values and compare them to
      # the student's answer
      foreach my $value (@{$correct}) {
         # this uses the currently active tolerance value 
         # (e.g., as set for the context or the specific Real MathObject)
         if (($value <=> $answer) == 0) {
            # WebWork interprets "score" as the number of correct
            # values in the student's answer. In this case, getting
            # one value correct should be treated as getting all of
            # them correct:
            $score = scalar(@{$correct});
            last;
         }
      }
      # if we get to here and the score is still 0, the
      # student's answer didn't match any of the correct values
      if ($score == 0 && ! $ansHash->{isPreview}) {
         push @errors, "Not correct";
      }
   }
   elsif (! $ansHash->{isPreview}) {
      push @errors, "You have to enter a single number";
   }
   return ($score, @errors);
}));

Context()->texStrings;
BEGIN_SOLUTION
According to Douglas Adams, the meaning of life is \( \{ $meaning_of_life->data->[1]
\} \). Of course, if you're a nihilist, it's \( \{ $meaning_of_life->data->[0] \} \);

END_SOLUTION
Context()->normalStrings;

ENDDOCUMENT();