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Bug #2802: partial credit multiple answers

    1: \label{Custom_Response_Problems}
    2: Custom Response is a way to have a problem graded based on an algorithm. The use of this response type is
    3: generally discouraged, since the responses will not be analyzable by the LON-CAPA statistics tools.
    4: 
    5: For a single textfield, the student's answer will be in a variable \$submission. If the Custom Response has multiple textfields, the answers will be in an array
    6: reference, and can be accessed as \$\$submission[0], \$\$submission[1], etc.
    7: 
    8: The student answer needs to be evaluated by Perl code inside the <answer>-tag. Custom Response needs to return a standard LON-CAPA. The most common response are:
    9: \begin{itemize}
   10: \item EXACT\_ANS: return if solved exactly correctly
   11: \item APPROX\_ANS: return if solved approximately
   12: \item INCORRECT: return if not correct, uses up a try
   13: \item ASSIGNED\_SCORE: partial credit (also return the credit factor, e.g. return(ASSIGNED\_SCORE,0.3);)
   14: \item SIG\_FAIL, NO\_UNIT, EXTRA\_ANSWER, MISSING\_ANSWER, BAD\_FORMULA, 
   15: WANTED\_NUMERIC: return if not correct for different reasons, does not use up a try
   16: \end{itemize}
   17: The answer display is shown instead of the student response in 'show answer' mode.
   18: The following example illustrates this:
   19: \begin{verbatim}
   20: <problem>
   21: <startouttext />Accept an answer of around 90 or -90<endouttext />
   22:   <customresponse answerdisplay="something near 90 or -90">
   23:     <answer type="loncapa/perl">
   24: # We do not want a vector
   25: if ($submission=~/\,/) { return 'EXTRA_ANSWER'; }
   26: # Need a numerical answer here
   27: if ($submission!~/^[\d\.\-\e]+$/i) { return 'WANTED_NUMERIC'; }
   28: $difference=abs(90-abs($submission));
   29: if ($difference==0) { return 'EXACT_ANS'; }
   30: if ($difference < 0.1) { return 'APPROX_ANS'; }
   31: return 'INCORRECT';</answer>
   32:     <textline readonly="no" />
   33:   </customresponse>
   34: </problem>
   35: \end{verbatim}
   36: 
   37: 
   38: Full list of possible return codes:
   39: \begin{itemize}
   40: \item EXACT\_ANS: student is exactly correct
   41: \item APPROX\_ANS:  student is approximately correct
   42: \item NO\_RESPONSE: student submitted no response
   43: \item MISSING\_ANSWER: student submitted some but not all parts of a response
   44: \item EXTRA\_ANSWER: student submitted a vector of values when a scalar was expected
   45: \item WANTED\_NUMERIC: expected a numeric answer and didn't get one
   46: \item SIG\_FAIL: incorrect number of Significant Figures
   47: \item UNIT\_FAIL: incorrect unit
   48: \item UNIT\_NOTNEEDED: submitted a unit when one shouldn't
   49: \item UNIT\_INVALID\_INSTRUCTOR: the unit provided by the author of the problem is unparsable
   50: \item UNIT\_INVALID\_STUDENT: the unit provided by the student is unparasable
   51: \item UNIT\_IRRECONCIBLE: the unit from the student and the instructor are of different types
   52: \item NO\_UNIT: needed a unit but none was submitted
   53: \item BAD\_FORMULA: syntax error in submitted formula
   54: \item INCORRECT: answer was wrong
   55: \item SUBMITTED: submission wasn't graded
   56: \item DRAFT: submission only stored
   57: \item MISORDERED\_RANK: student submitted a poorly order rank response
   58: \item ERROR: unable to get a grade
   59: \item ASSIGNED\_SCORE: partial credit; the customresponse needs to return the award followed by the partial credit factor  
   60: \item TOO\_LONG: answer submission was deemed too long
   61: \item INVALID\_FILETYPE: student tried to upload a file that was of an extension that was not specifically allowed 
   62: \item COMMA\_FAIL: answer requires the use of comma grouping and it wasn't provided or was incorrect
   63: \end{itemize}