IntervalEvaluators

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Revision as of 22:42, 14 February 2008

Interval Answer Checkers: PG Code Snippet

This code snippet shows the essential PG code to check intervals as student answers. 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.

Problem Techniques Index

PG problem file Explanation
  Context("Interval");
  # to allow open or closed intervals, uncomment
  #    the following line.
  # Context()->flags->set(ignoreEndpointTypes=>1);

  $int = Compute("(1,3)");

No changes are necessary in the tagging and description and initialization sections of the question file. In the problem set-up section of the file, we set the Context to be the Interval Context.

Once we're in the Interval context, we can define intervals as we'd expect: as shown here, or with limits at infinity:

  $int2 = Compute("(-inf,1]");

Would give the interval from negative infinity to 1, including the point at one. Note the Context flag to make endpoint checking "fuzzy."

  BEGIN_TEXT
  On what interval is the parabola
  \( y = (1-x)(x-3) \)
  above the \(x\)-axis?
  $BR
  For \(x\) in \{ ans_rule(15) \}
  END_TEXT

In the text section of the file, we ask the question as usual.

  ANS( $int->cmp() );

And in the answer and solution section of the file, we can check the answer using our interval MathObject.

Problem Techniques Index

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