questiontype.php

<?php  // $Id$
/**
* The default questiontype class.
*
* @version $Id$
* @author Martin Dougiamas and many others. This has recently been completely
*         rewritten by Alex Smith, Julian Sedding and Gustav Delius as part of
*         the Serving Mathematics project
*         {@link http://maths.york.ac.uk/serving_maths}
* @license http://www.gnu.org/copyleft/gpl.html GNU Public License
* @package quiz
*/

/// Question type class //////////////////////////////////////////////

class default_questiontype {

    /**
    * Name of the question type
    *
    * The name returned should coincide with the name of the directory
    * in which this questiontype is located
    * @ return string
    */
    function name() {
        return 'default';
    }

    /**
    * Saves or updates a question after editing by a teacher
    *
    * Given some question info and some data about the answers
    * this function parses, organises and saves the question
    * It is used by {@link question.php} when saving new data from
    * a form, and also by {@link import.php} when importing questions
    * This function in turn calls {@link save_question_options}
    * to save question-type specific options
    * @return object A {@link question} object
    * @param object $question   The question object which should be updated
    * @param object $form       The form submitted by the teacher
    * @param object $course     The course we are in
    */
    function save_question($question, $form, $course) {
        // This default implementation is suitable for most
        // question types.

        // First, save the basic question itself

        $question->name               = trim($form->name);
        $question->questiontext       = trim($form->questiontext);
        $question->questiontextformat = $form->questiontextformat;
        $question->parent             = isset($form->parent)? $form->parent : 0;
        $question->length = $this->actual_number_of_questions($question);
        $question->penalty = isset($form->penalty) ? $form->penalty : 0;

        if (empty($form->image)) {
            $question->image = "";
        } else {
            $question->image = $form->image;
        }

        if (empty($question->name)) {
            $question->name = substr(strip_tags($question->questiontext), 0, 15);
            if (empty($question->name)) {
                $question->name = '-';
            }
        }

        if ($question->penalty > 1 or $question->penalty < 0) {
            $question->errors['penalty'] = get_string('invalidpenalty', 'quiz');
        }

        if (isset($form->defaultgrade)) {
            $question->defaultgrade = $form->defaultgrade;
        }

        // Set the unique code
        // TODO: set the stamp to a hash of the questiondata so that identical
        // questions will get the same stamp. That will elliminate possible
        // duplication during backup when questions get changed without changes
        $question->stamp = make_unique_id_code();

        if (!empty($question->id)) { // Question already exists
            $question->version ++;    // Update version number of question
            if (!update_record("question", $question)) {
                error("Could not update question!");
            }
        } else {         // Question is a new one
            $question->version = 1;
            if (!$question->id = insert_record("question", $question)) {
                error("Could not insert new question!");
            }
        }

        // Now to save all the answers and type-specific options

        $form->id       = $question->id;
        $form->qtype    = $question->qtype;
        $form->category = $question->category;

        $result = $this->save_question_options($form);

        if (!empty($result->error)) {
            error($result->error);
        }

        if (!empty($result->notice)) {
            notice($result->notice, "question.php?id=$question->id");
        }

        if (!empty($result->noticeyesno)) {
            notice_yesno($result->noticeyesno, "question.php?id=$question->id", "edit.php");
            print_footer($course);
            exit;
        }

        return $question;
    }

    /**
    * Saves question-type specific options
    *
    * This is called by {@link save_question()} to save the question-type specific data
    * @return object $result->error or $result->noticeyesno or $result->notice
    * @param object $question  This holds the information from the editing form,
    *                          it is not a standard question object.
    */
    function save_question_options($question) {
        return null;
    }

    /**
    * Changes all states for the given attempts over to a new question
    *
    * This is used by the versioning code if the teacher requests that a question
    * gets replaced by the new version. In order for the attempts to be regraded
    * properly all data in the states referring to the old question need to be
    * changed to refer to the new version instead. In particular for question types
    * that use the answers table the answers belonging to the old question have to
    * be changed to those belonging to the new version.
    *
    * @param integer $oldquestionid  The id of the old question
    * @param object $newquestion    The new question
    * @param array  $attempts       An array of all attempt objects in whose states
    *                               replacement should take place
    */
    function replace_question_in_attempts($oldquestionid, $newquestion, $attemtps) {
        echo 'Not yet implemented';
        return;
    }

    /**
    * Loads the question type specific options for the question.
    *
    * This function loads any question type specific options for the
    * question from the database into the question object. This information
    * is placed in the $question->options field. A question type is
    * free, however, to decide on a internal structure of the options field.
    * @return bool            Indicates success or failure.
    * @param object $question The question object for the question. This object
    *                         should be updated to include the question type
    *                         specific information (it is passed by reference).
    */
    function get_question_options(&$question) {
        if (!isset($question->options)) {
            $question->options = new object;
        }
        // The default implementation attaches all answers for this question
        if (!$question->options->answers = get_records('question_answers', 'question',
         $question->id)) {
           //notify('Error: Missing question answers!');
           return false;
        }
        return true;
    }

    /**
    * Deletes states from the question-type specific tables
    *
    * @param string $stateslist  Comma separated list of state ids to be deleted
    */
    function delete_states($stateslist) {
        /// The default question type does not have any tables of its own
        // therefore there is nothing to delete

        return true;
    }

    /**
    * Deletes a question from the question-type specific tables
    *
    * @return boolean Success/Failure
    * @param object $question  The question being deleted
    */
    function delete_question($questionid) {
        /// The default question type does not have any tables of its own
        // therefore there is nothing to delete

        return true;
    }

    /**
    * Returns the number of question numbers which are used by the question
    *
    * This function returns the number of question numbers to be assigned
    * to the question. Most question types will have length one; they will be
    * assigned one number. The 'description' type, however does not use up a
    * number and so has a length of zero. Other question types may wish to
    * handle a bundle of questions and hence return a number greater than one.
    * @return integer         The number of question numbers which should be
    *                         assigned to the question.
    * @param object $question The question whose length is to be determined.
    *                         Question type specific information is included.
    */
    function actual_number_of_questions($question) {
        // By default, each question is given one number
        return 1;
    }

    /**
    * Creates empty session and response information for the question
    *
    * This function is called to start a question session. Empty question type
    * specific session data (if any) and empty response data will be added to the
    * state object. Session data is any data which must persist throughout the
    * attempt possibly with updates as the user interacts with the
    * question. This function does NOT create new entries in the database for
    * the session; a call to the {@link save_session_and_responses} member will
    * occur to do this.
    * @return bool            Indicates success or failure.
    * @param object $question The question for which the session is to be
    *                         created. Question type specific information is
    *                         included.
    * @param object $state    The state to create the session for. Note that
    *                         this will not have been saved in the database so
    *                         there will be no id. This object will be updated
    *                         to include the question type specific information
    *                         (it is passed by reference). In particular, empty
    *                         responses will be created in the ->responses
    *                         field.
    * @param object $cmoptions
    * @param object $attempt  The attempt for which the session is to be
    *                         started. Questions may wish to initialize the
    *                         session in different ways depending on the user id
    *                         or time available for the attempt.
    */
    function create_session_and_responses(&$question, &$state, $cmoptions, $attempt) {
        // The default implementation should work for the legacy question types.
        // Most question types with only a single form field for the student's response
        // will use the empty string '' as the index for that one response. This will
        // automatically be stored in and restored from the answer field in the
        // question_states table.
        $state->responses = array('' => '');
        return true;
    }

    /**
    * Restores the session data and most recent responses for the given state
    *
    * This function loads any session data associated with the question
    * session in the given state from the database into the state object.
    * In particular it loads the responses that have been saved for the given
    * state into the ->responses member of the state object.
    *
    * Question types with only a single form field for the student's response
    * will not need not restore the responses; the value of the answer
    * field in the question_states table is restored to ->responses['']
    * before this function is called. Question types with more response fields
    * should override this method and set the ->responses field to an
    * associative array of responses.
    * @return bool            Indicates success or failure.
    * @param object $question The question object for the question including any
    *                         question type specific information.
    * @param object $state    The saved state to load the session for. This
    *                         object should be updated to include the question
    *                         type specific session information and responses
    *                         (it is passed by reference).
    */
    function restore_session_and_responses(&$question, &$state) {
        // The default implementation does nothing (successfully)
        return true;
    }

    /**
    * Saves the session data and responses for the given question and state
    *
    * This function saves the question type specific session data from the
    * state object to the database. In particular for most question types it saves the
    * responses from the ->responses member of the state object. The question type
    * non-specific data for the state has already been saved in the question_states
    * table and the state object contains the corresponding id and
    * sequence number which may be used to index a question type specific table.
    *
    * Question types with only a single form field for the student's response
    * which is contained in ->responses[''] will not have to save this response,
    * it will already have been saved to the answer field of the question_states table.
    * Question types with more response fields should override this method and save
    * the responses in their own database tables.
    * @return bool            Indicates success or failure.
    * @param object $question The question object for the question including
    *                         the question type specific information.
    * @param object $state    The state for which the question type specific
    *                         data and responses should be saved.
    */
    function save_session_and_responses(&$question, &$state) {
        // The default implementation does nothing (successfully)
        return true;
    }

    /**
    * Returns an array of values which will give full marks if graded as
    * the $state->responses field
    *
    * The correct answer to the question in the given state, or an example of
    * a correct answer if there are many, is returned. This is used by some question
    * types in the {@link grade_responses()} function but it is also used by the
    * question preview screen to fill in correct responses.
    * @return mixed           A response array giving the responses corresponding
    *                         to the (or a) correct answer to the question. If there is
    *                         no correct answer that scores 100% then null is returned.
    * @param object $question The question for which the correct answer is to
    *                         be retrieved. Question type specific information is
    *                         available.
    * @param object $state    The state of the question, for which a correct answer is
    *                         needed. Question type specific information is included.
    */
    function get_correct_responses(&$question, &$state) {
        /* The default implementation returns the response for the first answer
        that gives full marks. */
        if ($question->options->answers) {
            foreach ($question->options->answers as $answer) {
                if (((int) $answer->fraction) === 1) {
                    return array('' => $answer->answer);
                }
            }
        }
        return null;
    }

    /**
    * Return an array of values with the texts for all possible responses stored
    * for the question
    *
    * All answers are found and their text values isolated
    * @return object          A mixed object
    *             ->id        question id. Needed to manage random questions:
    *                         it's the id of the actual question presented to user in a given attempt
    *             ->responses An array of values giving the responses corresponding
    *                         to all answers to the question. Answer ids are used as keys.
    *                         The text and partial credit are the object components
    * @param object $question The question for which the answers are to
    *                         be retrieved. Question type specific information is
    *                         available.
    */
    // ULPGC ecastro
    function get_all_responses(&$question, &$state) {
        unset($answers);
        if (is_array($question->options->answers)) {
            foreach ($question->options->answers as $aid=>$answer) {
                unset ($r);
                $r->answer = $answer->answer;
                $r->credit = $answer->fraction;
                $answers[$aid] = $r;
            }
        } else {
            $answers[]="error"; // just for debugging, eliminate
        }
        $result->id = $question->id;
        $result->responses = $answers;
        return $result;
    }

    /**
    * Return the actual response to the question in a given state
    * for the question
    *
    * @return mixed           An array containing the response or reponses (multiple answer, match)
    *                         given by the user in a particular attempt.
    * @param object $question The question for which the correct answer is to
    *                         be retrieved. Question type specific information is
    *                         available.
    * @param object $state    The state object that corresponds to the question,
    *                         for which a correct answer is needed. Question
    *                         type specific information is included.
    */
    // ULPGC ecastro
    function get_actual_response($question, $state) {
       // change length to truncate responses here if you want
       $lmax = 40;
       if (!empty($state->responses)) {
              $responses[] = (strlen($state->responses['']) > $lmax) ?
               substr($state->responses[''], 0, $lmax).'...' : $state->responses[''];
       } else {
           $responses[] = '';
       }
       return $responses;
    }

    // ULPGC ecastro
    function get_fractional_grade(&$question, &$state) {
        $maxgrade = $question->maxgrade;
        $grade = $state->grade;
        if ($maxgrade) {
            return (float)($grade/$maxgrade);
        } else {
            return (float)$grade;
        }
    }


    /**
    * Checks if the response given is correct and returns the id
    *
    * @return int             The ide number for the stored answer that matches the response
    *                         given by the user in a particular attempt.
    * @param object $question The question for which the correct answer is to
    *                         be retrieved. Question type specific information is
    *                         available.
    * @param object $state    The state object that corresponds to the question,
    *                         for which a correct answer is needed. Question
    *                         type specific information is included.
    */
    // ULPGC ecastro
    function check_response(&$question, &$state){
        return false;
    }

    /**
    * Prints the question including the number, grading details, content,
    * feedback and interactions
    *
    * This function prints the question including the question number,
    * grading details, content for the question, any feedback for the previously
    * submitted responses and the interactions. The default implementation calls
    * various other methods to print each of these parts and most question types
    * will just override those methods.
    * @param object $question The question to be rendered. Question type
    *                         specific information is included. The
    *                         maximum possible grade is in ->maxgrade. The name
    *                         prefix for any named elements is in ->name_prefix.
    * @param object $state    The state to render the question in. The grading
    *                         information is in ->grade, ->raw_grade and
    *                         ->penalty. The current responses are in
    *                         ->responses. This is an associative array (or the
    *                         empty string or null in the case of no responses
    *                         submitted). The last graded state is in
    *                         ->last_graded (hence the most recently graded
    *                         responses are in ->last_graded->responses). The
    *                         question type specific information is also
    *                         included.
    * @param integer $number  The number for this question.
    * @param object $cmoptions
    * @param object $options  An object describing the rendering options.
    */
    function print_question(&$question, &$state, $number, $cmoptions, $options) {
        /* The default implementation should work for most question types
        provided the member functions it calls are overridden where required.
        The layout is determined by the template question.html */
        global $CFG;

        // For editing teachers print a link to an editing popup window
        $editlink = '';
        if (isteacheredit($cmoptions->course)) {
            $stredit = get_string('edit');
            $linktext = '<img src="'.$CFG->pixpath.'/t/edit.gif" border="0" alt="'.$stredit.'" />';
            $editlink = link_to_popup_window('/question/question.php?id='.$question->id, $stredit, $linktext, 450, 550, $stredit, '', true);
        }

        $grade = '';
        if ($question->maxgrade and $options->scores) {
            if ($cmoptions->optionflags & QUESTION_ADAPTIVE) {
                $grade = (!question_state_is_graded($state->last_graded)) ? '--/' : round($state->last_graded->grade, $cmoptions->decimalpoints).'/';
            }
            $grade .= $question->maxgrade;
        }
        
        $comment = $state->comment;
        $commentlink = '';
        if (isset($options->questioncommentlink)) {
            $strcomment = get_string('commentorgrade', 'quiz');
            $commentlink = '<div class="commentlink">'.link_to_popup_window ($options->questioncommentlink.'?attempt='.$state->attempt.'&amp;question='.$question->id,
                             'commentquestion', $strcomment, 450, 650, $strcomment, 'none', true).'</div>';
        }

        $history = $this->history($question, $state, $number, $cmoptions, $options);

        include "$CFG->dirroot/question/type/question.html";
    }

    /*
     * Print history of responses
     *
     * Used by print_question()
     */
    function history($question, $state, $number, $cmoptions, $options) {
        $history = '';
        if(isset($options->history) and $options->history) {
            if ($options->history == 'all') {
                // show all states
                $states = get_records_select('question_states', "attempt = '$state->attempt' AND question = '$question->id' AND event > '0'", 'seq_number ASC');
            } else {
                // show only graded states
                $states = get_records_select('question_states', "attempt = '$state->attempt' AND question = '$question->id' AND event IN (".QUESTION_EVENTGRADE.','.QUESTION_EVENTCLOSEANDGRADE.")", 'seq_number ASC');
            }
            if (count($states) > 1) {
                $strreviewquestion = get_string('reviewresponse', 'quiz');
                unset($table);
                $table->head  = array (
                    get_string('numberabbr', 'quiz'),
                    get_string('action', 'quiz'),
                    get_string('response', 'quiz'),
                    get_string('time'),
                    get_string('score', 'quiz'),
                    //get_string('penalty', 'quiz'),
                    get_string('grade', 'quiz'),
                );
                $table->width = '100%';
                foreach ($states as $st) {
                    $st->responses[''] = $st->answer;
                    $this->restore_session_and_responses($question, $st);
                    $b = ($state->id == $st->id) ? '<b>' : '';
                    $be = ($state->id == $st->id) ? '</b>' : '';
                    if ($state->id == $st->id) {
                        $link = '<b>'.$st->seq_number.'</b>';
                    } else {
                        if(isset($options->questionreviewlink)) {
                            $link = link_to_popup_window ($options->questionreviewlink.'?state='.$st->id.'&amp;number='.$number,
                             'reviewquestion', $st->seq_number, 450, 650, $strreviewquestion, 'none', true);
                        } else {
                            $link = $st->seq_number;
                        }
                    }
                    $table->data[] = array (
                        $link,
                        $b.get_string('event'.$st->event, 'quiz').$be,
                        $b.$this->response_summary($question, $st).$be,
                        $b.userdate($st->timestamp, get_string('timestr', 'quiz')).$be,
                        $b.round($st->raw_grade, $cmoptions->decimalpoints).$be,
                        //$b.round($st->penalty, $cmoptions->decimalpoints).$be,
                        $b.round($st->grade, $cmoptions->decimalpoints).$be
                    );
                }
                $history = make_table($table);
            }
        }
        return $history;
    }


    /**
    * Prints the score obtained and maximum score available plus any penalty
    * information
    *
    * This function prints a summary of the scoring in the most recently
    * graded state (the question may not have been submitted for marking at
    * the current state). The default implementation should be suitable for most
    * question types.
    * @param object $question The question for which the grading details are
    *                         to be rendered. Question type specific information
    *                         is included. The maximum possible grade is in
    *                         ->maxgrade.
    * @param object $state    The state. In particular the grading information
    *                          is in ->grade, ->raw_grade and ->penalty.
    * @param object $cmoptions
    * @param object $options  An object describing the rendering options.
    */
    function print_question_grading_details(&$question, &$state, $cmoptions, $options) {
        /* The default implementation prints the number of marks if no attempt
        has been made. Otherwise it displays the grade obtained out of the
        maximum grade available and a warning if a penalty was applied for the
        attempt and displays the overall grade obtained counting all previous
        responses (and penalties) */

        if (QUESTION_EVENTDUPLICATE == $state->event) {
            echo ' ';
            print_string('duplicateresponse', 'quiz');
        }
        if (!empty($question->maxgrade) && $options->scores) {
            if (question_state_is_graded($state->last_graded)) {
                // Display the grading details from the last graded state
                $grade->cur = round($state->last_graded->grade, $cmoptions->decimalpoints);
                $grade->max = $question->maxgrade;
                $grade->raw = round($state->last_graded->raw_grade, $cmoptions->decimalpoints);

                // let student know wether the answer was correct
                echo '<div class="correctness ';
                if ($state->last_graded->raw_grade >= $question->maxgrade/1.01) { // We divide by 1.01 so that rounding errors dont matter.
                    echo ' correct">';
                    print_string('correct', 'quiz');
                } else if ($state->last_graded->raw_grade > 0) {
                    echo ' partiallycorrect">';
                    print_string('partiallycorrect', 'quiz');
                } else {
                    echo ' incorrect">';
                    print_string('incorrect', 'quiz');
                }
                echo '</div>';

                echo '<div class="gradingdetails">';
                // print grade for this submission
                print_string('gradingdetails', 'quiz', $grade);
                if ($cmoptions->penaltyscheme) {
                    // print details of grade adjustment due to penalties
                    if ($state->last_graded->raw_grade > $state->last_graded->grade){
                        print_string('gradingdetailsadjustment', 'quiz', $grade);
                    }
                    // print info about new penalty
                    // penalty is relevant only if the answer is not correct and further attempts are possible
                    if (($state->last_graded->raw_grade < $question->maxgrade) and (QUESTION_EVENTCLOSEANDGRADE !== $state->event)) {
                        if ('' !== $state->last_graded->penalty && ((float)$state->last_graded->penalty) > 0.0) {
                            // A penalty was applied so display it
                            print_string('gradingdetailspenalty', 'quiz', $state->last_graded->penalty);
                        } else {
                            /* No penalty was applied even though the answer was
                            not correct (eg. a syntax error) so tell the student
                            that they were not penalised for the attempt */
                            print_string('gradingdetailszeropenalty', 'quiz');
                        }
                    }
                }
                echo '</div>';
            }
        }
    }

    /**
    * Prints the main content of the question including any interactions
    *
    * This function prints the main content of the question including the
    * interactions for the question in the state given. The last graded responses
    * are printed or indicated and the current responses are selected or filled in.
    * Any names (eg. for any form elements) are prefixed with $question->name_prefix.
    * This method is called from the print_question method.
    * @param object $question The question to be rendered. Question type
    *                         specific information is included. The name
    *                         prefix for any named elements is in ->name_prefix.
    * @param object $state    The state to render the question in. The grading
    *                         information is in ->grade, ->raw_grade and
    *                         ->penalty. The current responses are in
    *                         ->responses. This is an associative array (or the
    *                         empty string or null in the case of no responses
    *                         submitted). The last graded state is in
    *                         ->last_graded (hence the most recently graded
    *                         responses are in ->last_graded->responses). The
    *                         question type specific information is also
    *                         included.
    *                         The state is passed by reference because some adaptive
    *                         questions may want to update it during rendering
    * @param object $cmoptions
    * @param object $options  An object describing the rendering options.
    */
    function print_question_formulation_and_controls(&$question, &$state, $cmoptions, $options) {
        /* This default implementation prints an error and must be overridden
        by all question type implementations, unless the default implementation
        of print_question has been overridden. */

        notify('Error: Question formulation and input controls has not'
               .'  been implemented for question type '.$this->name());
    }

    /**
    * Prints the submit button(s) for the question in the given state
    *
    * This function prints the submit button(s) for the question in the
    * given state. The name of any button created will be prefixed with the
    * unique prefix for the question in $question->name_prefix. The suffix
    * 'submit' is reserved for the single question submit button and the suffix
    * 'validate' is reserved for the single question validate button (for
    * question types which support it). Other suffixes will result in a response
    * of that name in $state->responses which the printing and grading methods
    * can then use.
    * @param object $question The question for which the submit button(s) are to
    *                         be rendered. Question type specific information is
    *                         included. The name prefix for any
    *                         named elements is in ->name_prefix.
    * @param object $state    The state to render the buttons for. The
    *                         question type specific information is also
    *                         included.
    * @param object $cmoptions
    * @param object $options  An object describing the rendering options.
    */
    function print_question_submit_buttons(&$question, &$state, $cmoptions, $options) {
        /* The default implementation should be suitable for most question
        types. It prints a mark button in the case where individual marking is
        allowed. */

        if (($cmoptions->optionflags & QUESTION_ADAPTIVE) and !$options->readonly) {
            echo '<input type="submit" name="';
            echo $question->name_prefix;
            echo 'submit" value="';
            print_string('mark', 'quiz');
            echo '" class="submit btn"';
            echo ' />';
        }
    }


    /**
    * Return a summary of the student response
    *
    * This function returns a short string of no more than a given length that
    * summarizes the student's response in the given $state. This is used for
    * example in the response history table
    * @return string         The summary of the student response
    * @param object $question 
    * @param object $state   The state whose responses are to be summarized
    * @param int $length     The maximum length of the returned string
    */
    function response_summary($question, $state, $length=80) {
        // This should almost certainly be overridden
        return substr(implode(',', $this->get_actual_response($question, $state)), 0, $length);
    }

    /**
    * Renders the question for printing and returns the LaTeX source produced
    *
    * This function should render the question suitable for a printed problem
    * or solution sheet in LaTeX and return the rendered output.
    * @return string          The LaTeX output.
    * @param object $question The question to be rendered. Question type
    *                         specific information is included.
    * @param object $state    The state to render the question in. The
    *                         question type specific information is also
    *                         included.
    * @param object $cmoptions
    * @param string $type     Indicates if the question or the solution is to be
    *                         rendered with the values 'question' and
    *                         'solution'.
    */
    function get_texsource(&$question, &$state, $cmoptions, $type) {
        // The default implementation simply returns a string stating that
        // the question is only available online.

        return get_string('onlineonly', 'texsheet');
    }

    /**
    * Compares two question states for equivalence of the student's responses
    *
    * The responses for the two states must be examined to see if they represent
    * equivalent answers to the question by the student. This method will be
    * invoked for each of the previous states of the question before grading
    * occurs. If the student is found to have already attempted the question
    * with equivalent responses then the attempt at the question is ignored;
    * grading does not occur and the state does not change. Thus they are not
    * penalized for this case.
    * @return boolean
    * @param object $question  The question for which the states are to be
    *                          compared. Question type specific information is
    *                          included.
    * @param object $state     The state of the question. The responses are in
    *                          ->responses.
    * @param object $teststate The state whose responses are to be
    *                          compared. The state will be of the same age or
    *                          older than $state.
    */
    function compare_responses(&$question, $state, $teststate) {
        // The default implementation performs a comparison of the response
        // arrays. The ordering of the arrays does not matter.
        // Question types may wish to override this (eg. to ignore trailing
        // white space or to make "7.0" and "7" compare equal).
        return $state->responses == $teststate->responses;
    }

    /**
    * Checks whether a response matches a given answer
    *
    * This method only applies to questions that use teacher-defined answers
    *
    * @return boolean
    */
    function test_response(&$question, &$state, $answer) {
        $response = isset($state->responses['']) ? $state->responses[''] : '';
        return ($response == $answer->answer);
    }

    /**
    * Performs response processing and grading
    *
    * This function performs response processing and grading and updates
    * the state accordingly.
    * @return boolean         Indicates success or failure.
    * @param object $question The question to be graded. Question type
    *                         specific information is included.
    * @param object $state    The state of the question to grade. The current
    *                         responses are in ->responses. The last graded state
    *                         is in ->last_graded (hence the most recently graded
    *                         responses are in ->last_graded->responses). The
    *                         question type specific information is also
    *                         included. The ->raw_grade and ->penalty fields
    *                         must be updated. The method is able to
    *                         close the question session (preventing any further
    *                         attempts at this question) by setting
    *                         $state->event to QUESTION_EVENTCLOSEANDGRADE
    * @param object $cmoptions
    */
    function grade_responses(&$question, &$state, $cmoptions) {
        /* The default implementation uses the comparison method to check if
        the responses given are equivalent to the responses for each answer
        in turn and sets the marks and penalty accordingly. This works for the
        most simple question types. */

        $teststate = clone($state);
        $teststate->raw_grade = 0;
        foreach($question->options->answers as $answer) {
            $teststate->responses[''] = $answer->answer;

            if($this->compare_responses($question, $state, $teststate)) {
                $state->raw_grade = min(max((float) $answer->fraction,
                 0.0), 1.0) * $question->maxgrade;
                break;
            }
        }
        if (empty($state->raw_grade)) {
            $state->raw_grade = 0.0;
        }
        // Only allow one attempt at the question
        $state->penalty = 1;

        // mark the state as graded
        $state->event = ($state->event ==  QUESTION_EVENTCLOSE) ? QUESTION_EVENTCLOSEANDGRADE : QUESTION_EVENTGRADE;

        return true;
    }


    /**
    * Includes configuration settings for the question type on the quiz admin
    * page
    *
    * TODO: It makes no sense any longer to do the admin for question types
    * from the quiz admin page. This should be changed.
    * Returns an array of objects describing the options for the question type
    * to be included on the quiz module admin page.
    * Configuration options can be included by setting the following fields in
    * the object:
    * ->name           The name of the option within this question type.
    *                  The full option name will be constructed as
    *                  "quiz_{$this->name()}_$name", the human readable name
    *                  will be displayed with get_string($name, 'quiz').
    * ->code           The code to display the form element, help button, etc.
    *                  i.e. the content for the central table cell. Be sure
    *                  to name the element "quiz_{$this->name()}_$name" and
    *                  set the value to $CFG->{"quiz_{$this->name()}_$name"}.
    * ->help           Name of the string from the quiz module language file
    *                  to be used for the help message in the third column of
    *                  the table. An empty string (or the field not set)
    *                  means to leave the box empty.
    * Links to custom settings pages can be included by setting the following
    * fields in the object:
    * ->name           The name of the link text string.
    *                  get_string($name, 'quiz') will be called.
    * ->link           The filename part of the URL for the link. The full URL
    *                  is contructed as
    *                  "$CFG->wwwroot/question/type/{$this->name()}/$link?sesskey=$sesskey"
    *                  [but with the relavant calls to the s and rawurlencode
    *                  functions] where $sesskey is the sesskey for the user.
    * @return array    Array of objects describing the configuration options to
    *                  be included on the quiz module admin page.
    */
    function get_config_options() {
        // No options by default

        return false;
    }

    /**
    * Returns true if the editing wizard is finished, false otherwise.
    *
    * The default implementation returns true, which is suitable for all question-
    * types that only use one editing form. This function is used in
    * question.php to decide whether we can regrade any states of the edited
    * question and redirect to edit.php.
    *
    * The dataset dependent question-type, which is extended by the calculated
    * question-type, overwrites this method because it uses multiple pages (i.e.
    * a wizard) to set up the question and associated datasets.
    *
    * @param object $form  The data submitted by the previous page.
    *
    * @return boolean      Whether the wizard's last page was submitted or not.
    */
    function finished_edit_wizard(&$form) {
        //In the default case there is only one edit page.
        return true;
    }

    /**
    * Prints a table of course modules in which the question is used
    *
    * TODO: This should be made quiz-independent
    *
    * This function is used near the end of the question edit forms in all question types
    * It prints the table of quizzes in which the question is used
    * containing checkboxes to allow the teacher to replace the old question version
    *
    * @param object $question
    * @param object $course
    * @param integer $cmid optional The id of the course module currently being edited
    */
    function print_replacement_options($question, $course, $cmid='0') {

        // Disable until the versioning code has been fixed
        return;

        // no need to display replacement options if the question is new
        if(empty($question->id)) {
            return true;
        }

        // get quizzes using the question (using the question_instances table)
        $quizlist = array();
        if(!$instances = get_records('quiz_question_instances', 'question', $question->id)) {
            $instances = array();
        }
        foreach($instances as $instance) {
            $quizlist[$instance->quiz] = $instance->quiz;
        }
        $quizlist = implode(',', $quizlist);
        if(empty($quizlist) or !$quizzes = get_records_list('quiz', 'id', $quizlist)) {
            $quizzes = array();
        }

        // do the printing
        if(count($quizzes) > 0) {
            // print the table
            $strquizname  = get_string('modulename', 'quiz');
            $strdoreplace = get_string('replace', 'quiz');
            $straffectedstudents = get_string('affectedstudents', 'quiz', $course->students);
            echo "<tr valign=\"top\">\n";
            echo "<td align=\"right\"><b>".get_string("replacementoptions", "quiz").":</b></td>\n";
            echo "<td align=\"left\">\n";
            echo "<table cellpadding=\"5\" align=\"left\" class=\"generalbox\" width=\"100%\">\n";
            echo "<tr>\n";
            echo "<th align=\"left\" valign=\"top\" nowrap=\"nowrap\" class=\"generaltableheader c0\">$strquizname</th>\n";
            echo "<th align=\"center\" valign=\"top\" nowrap=\"nowrap\" class=\"generaltableheader c0\">$strdoreplace</th>\n";
            echo "<th align=\"left\" valign=\"top\" nowrap=\"nowrap\" class=\"generaltableheader c0\">$straffectedstudents</th>\n";
            echo "</tr>\n";
            foreach($quizzes as $quiz) {
                // work out whethere it should be checked by default
                $checked = '';
                if((int)$cmid === (int)$quiz->id
                    or empty($quiz->usercount)) {
                    $checked = "checked=\"checked\"";
                }

                // find how many different students have already attempted this quiz
                $students = array();
                if($attempts = get_records_select('quiz_attempts', "quiz = '$quiz->id' AND preview = '0'")) {
                    foreach($attempts as $attempt) {
                        if (record_exists('question_states', 'attempt', $attempt->uniqueid, 'question', $question->id, 'originalquestion', 0)) {
                            $students[$attempt->userid] = 1;
                        }
                    }
                }
                $studentcount = count($students);

                $strstudents = $studentcount === 1 ? $course->student : $course->students;
                echo "<tr>\n";
                echo "<td align=\"left\" class=\"generaltablecell c0\">".format_string($quiz->name)."</td>\n";
                echo "<td align=\"center\" class=\"generaltablecell c0\"><input name=\"q{$quiz->id}replace\" type=\"checkbox\" ".$checked." /></td>\n";
                echo "<td align=\"left\" class=\"generaltablecell c0\">".(($studentcount) ? $studentcount.' '.$strstudents : '-')."</td>\n";
                echo "</tr>\n";
            }
            echo "</table>\n";
        }
        echo "</td></tr>\n";
    }

    function print_question_form_end($question, $submitscript='') {
    // This function is used at the end of the question edit forms in all question types
    // It prints the submit, copy, and cancel buttons and the standard hidden form fields
        global $USER;
        echo '<tr valign="top">
              <td colspan="2" align="center">
              <input type="submit" '.$submitscript.' value="'.get_string('savechanges').'" /> ';
        if ($question->id) {
            echo '<input type="submit" name="makecopy" '.$submitscript.' value="'.get_string("makecopy", "quiz").'" /> ';
        }
        echo '<input type="submit" name="cancel" value="'.get_string("cancel").'" />
              <input type="hidden" name="sesskey" value="'.$USER->sesskey.'" />
              <input type="hidden" name="id" value="'.$question->id.'" />
              <input type="hidden" name="qtype" value="'.$question->qtype.'" />';
        // The following hidden field indicates that the versioning code should be turned on, i.e.,
        // that old versions should be kept if necessary
        echo '<input type="hidden" name="versioning" value="on" />
              </td></tr>';
    }
    
/// BACKUP FUNCTIONS ////////////////////////////

    /*
     * Backup the data in the question
     *
     * This is used in question/backuplib.php
     */
    function backup($bf,$preferences,$question,$level=6) {
        // The default type has nothing to back up
        return true;
    }

/// RESTORE FUNCTIONS /////////////////

    /*
     * Restores the data in the question
     *
     * This is used in question/restorelib.php
     */
    function restore($old_question_id,$new_question_id,$info,$restore) {
        // The default question type has nothing to restore
        return true;
    }

    function restore_map($old_question_id,$new_question_id,$info,$restore) {
        // There is nothing to decode
        return true;
    }

    function restore_recode_answer($state, $restore) {
        // There is nothing to decode
        return $state->answer;
    }    

    //This function restores the question_rqp_states
    function restore_state($state_id,$info,$restore) {
        // The default question type does not keep its own state information
        return true;
    }

}

?>