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    1: \label{Custom_Response_Problem_Creation}\index{Custom Response}
    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 \texttt{$<$ answer$>$}-tag. Custom Response needs to include an algorithm that determines and returns a standard LON-CAPA response. The most common LON-CAPA responses 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, \\
   14: e.g. return(ASSIGNED\_SCORE,0.3);)
   15: \item SIG\_FAIL, NO\_UNIT, EXTRA\_ANSWER, MISSING\_ANSWER, BAD\_FORMULA, 
   16: WANTED\_NUMERIC, WRONG\_FORMAT: return if not correct for different reasons, does not use up a try
   17: \end{itemize}
   18: The \texttt{answerdisplay} is shown instead of the student response in `show answer' mode after the answer date.
   19: The following example illustrates this:
   20: \begin{verbatim}
   21: <problem>
   22: <startouttext />Accept an answer of around 90 or -90<endouttext />
   23:   <customresponse answerdisplay="something near 90 or -90">
   24:     <answer type="loncapa/perl">
   25: # This examples uses perl 'regular expressions' for string evaluation. 
   26: # Consult a perl reference for help understanding the regular expressions.
   27: # We do not want a vector
   28: if ($submission=~/\,/) { return 'EXTRA_ANSWER'; }
   29: # Need a numerical answer here
   30: if ($submission!~/^[\d\.\-\e]+$/i) { return 'WANTED_NUMERIC'; }
   31: $difference=abs(90-abs($submission));
   32: if ($difference==0) { return 'EXACT_ANS'; }
   33: if ($difference < 0.1) { return 'APPROX_ANS'; }
   34: return 'INCORRECT';</answer>
   35:     <textline readonly="no" />
   36:   </customresponse>
   37: </problem>
   38: \end{verbatim}
   39: 
   40: 
   41: Full list of possible return codes:
   42: \begin{itemize}
   43: \item EXACT\_ANS: student is exactly correct
   44: \item APPROX\_ANS:  student is approximately correct
   45: \item NO\_RESPONSE: student submitted no response
   46: \item MISSING\_ANSWER: student submitted some but not all parts of a response
   47: \item EXTRA\_ANSWER: student submitted a vector of values when a scalar was expected
   48: \item WANTED\_NUMERIC: expected a numeric answer and didn't get one
   49: \item SIG\_FAIL: incorrect number of Significant Figures
   50: \item UNIT\_FAIL: incorrect unit
   51: \item UNIT\_NOTNEEDED: submitted a unit when one shouldn't
   52: \item UNIT\_INVALID\_INSTRUCTOR: the unit provided by the author of the problem is unparsable
   53: \item UNIT\_INVALID\_STUDENT: the unit provided by the student is unparasable
   54: \item UNIT\_IRRECONCIBLE: the unit from the student and the instructor are of different types
   55: \item NO\_UNIT: needed a unit but none was submitted
   56: \item BAD\_FORMULA: syntax error in submitted formula
   57: \item WRONG\_FORMAT: student submission did not have the expected format
   58: \item INCORRECT: answer was wrong
   59: \item SUBMITTED: submission wasn't graded
   60: \item DRAFT: submission only stored
   61: \item MISORDERED\_RANK: student submitted a poorly order rank response
   62: \item ERROR: unable to get a grade
   63: \item ASSIGNED\_SCORE: partial credit; the customresponse needs to return the award followed by the partial credit factor  
   64: \item TOO\_LONG: answer submission was deemed too long
   65: \item INVALID\_FILETYPE: student tried to upload a file that was of an extension that was not specifically allowed 
   66: \item EXCESS\_FILESIZE: student uploaded file(s) with a combined size that exceeded the amount allowed
   67: \item COMMA\_FAIL: answer requires the use of comma grouping and it wasn't provided or was incorrect
   68: \end{itemize}