ConstantsInProblems

Named Numerical Constants (Parameters) in Problems: PG Code Snippet

This code snippet shows the essential PG code to include named constants in a WeBWorK problem. Note that these are insertions, not a complete PG file. This code will have to be incorporated into the problem file on which you are working.

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PG problem file	Explanation
Context("Numeric"); Context()->constants->add(k=>0.01); # this means that student answers are # not reduced to the numerical value # specified in the Context Context()->flags->set( formatStudentAnswer=>'parsed' );	No changes are needed in the tagging and description or initialization sections of the problem file. In the problem set-up section, we add to the Context the constants we're going to use. Here we define a constant k, and assign it a value that will be used when expressions involving k are evaluated. Do not set k=1, because if you do, then kx and x/k are equivalent, for example. Obviously, do not set k=0. In this case we specified constants->add(), so that the constant k is added to existing constants in the problem. If we had used constants->are(), we would also remove all predefined constants from the Context (in a manner similar to the use of variables->add() and variables->are() when defining variables in a problem. One other tweak that we might want to put in here is to reset a Context flag so that students' answers are not reduced to numerical values when they are previewed or submitted. This is done by setting the formatStudentAnswer flag, as shown.
BEGIN_TEXT \(f(x) = x-k\) (where \(k>0\) is constant) is zero when $BR \(x = \)\{ ans_rule(15) \} END_TEXT	In the text section of the problem we then ask a question involving the constant.
ANS( Compute("k")->cmp() );	And in the answer and solution section of the file we can refer to the constant in the solution to the problem.

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