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  1. Moodle
  2. MDL-8473 Numerical question: bugs and improvements
  3. MDL-8478

Small numerical naswers i.e. 1e-18 are not graded correctly

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    Details

    • Type: Sub-task
    • Status: Closed
    • Priority: Minor
    • Resolution: Fixed
    • Affects Version/s: 1.8
    • Fix Version/s: None
    • Component/s: Questions
    • Labels:
      None
    • Affected Branches:
      MOODLE_18_STABLE

      Description

      When the answer is a small number i.e 1e-19 as the charge of the electron the range of the allowed answer can extend to negative value given the fact that the code of add +- a small number
      line 355 of numerical/questiontype.php in the function get_tolerance_interval(&$answer) {
      // We need to add a tiny fraction depending on the set precision to make the
      // comparison work correctly. Otherwise seemingly equal values can yield
      // false. (fixes bug #3225)
      $tolerance = (float)$answer->tolerance + ("1.0e-".ini_get('precision'));
      This is to remediate for the 0.000000001 or .999999999 possible output of real number functions.
      So if the user put an answer like 1.6e-5 php code could sometimes see it 0.0000159999999 or 0.00001600000001
      for small answer values the tiny fraction should be calcualted as a fraction of the number and not an absolute value
      actually ("1.0e-".ini_get('precision')); can gives something like 1e-13 for a precision of 8 .
      After completing tests, a working solution will be proposed soon

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              Assignee:
              timhunt Tim Hunt
              Reporter:
              ppichet Pierre Pichet
              Tester:
              Nobody
              Participants:
              Component watchers:
              Tim Hunt, Andrew Nicols, Jun Pataleta, Michael Hawkins, Shamim Rezaie, Simey Lameze
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                Created:
                Updated:
                Resolved: