Two solutions using Context("Inequalities")

[d-torrance]

Hello!

Consider the following problem:

DOCUMENT();

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

Context("Inequalities");

$ans = Compute("x=1 or x=2");

TEXT(beginproblem());
BEGIN_TEXT
\{ ans_rule(20) \}
END_TEXT

ANS($ans->cmp());

ENDDOCUMENT();

The solution "{1,2}" is marked correct, but "x=1 or x=2" (which we used to define the answer in the first place) is marked incorrect.

This is an issue for many of the problems in [1].

[1] https://github.com/openwebwork/webwork-open-problem-library/tree/master/OpenProblemLibrary/CollegeOfIdaho/setAlgebra_04_03_AbsoluteValue

[dpvc]

The x=1 or x=2 expression is supposed to produce a Set object equivalent to {1,2}, but it turns out that it is producing a Union object (with one element, the set {1,2}). Due to some technical issues in how Union's are checked, this causes the correct answer to be marked incorrect. It is easily fixed in the lib/Value/Set.pm file, but until that is is an official release, one way to handle it in the problem itself is to add

$ans = $ans->{data}[0] if $ans->type eq "Union";  # hack to fix problem with inequality above

directly after the line that computes $ans. That will fix it for now, and when the library is fixed, the if statement will be false, and it will stop doing anything. So the problem should continue to work without modification (though it would be good to remove the hack eventually).

[dpvc]

The issue280 branch of my fork of PG includes the fix.

[dpvc]

The branch has been merged into develop.