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1 : sh002i 440 ################################################################################
2 : sh002i 494 # WeBWorK mod_perl (c) 2000-2002 WeBWorK Project
3 : sh002i 440 # $Id$
4 :     ################################################################################
5 :    
6 : sh002i 424 package WeBWorK::PG;
7 : sh002i 414
8 : sh002i 455 =head1 NAME
9 :    
10 : sh002i 476 WeBWorK::PG - Wrap the action of the PG Translator in an easy-to-use API.
11 : sh002i 455
12 :     =cut
13 :    
14 : sh002i 414 use strict;
15 :     use warnings;
16 : sh002i 555 use File::Path qw(rmtree);
17 : sh002i 526 use File::Temp qw(tempdir);
18 : sh002i 414 use WeBWorK::DB::Classlist;
19 :     use WeBWorK::DB::WW;
20 :     use WeBWorK::PG::Translator;
21 : sh002i 492 use WeBWorK::Problem;
22 : sh002i 455 use WeBWorK::Utils qw(readFile formatDateTime);
23 : sh002i 414
24 : sh002i 424 sub new($$$$$$$$) {
25 : sh002i 415 my $invocant = shift;
26 :     my $class = ref($invocant) || $invocant;
27 : sh002i 424 my (
28 :     $courseEnv,
29 : sh002i 502 $user,
30 : sh002i 424 $key,
31 : sh002i 502 $set,
32 :     $problem,
33 :     $psvn,
34 :     $formFields, # in CGI::Vars format
35 : sh002i 424 $translationOptions, # hashref containing options for the
36 :     # translator, such as whether to show
37 :     # hints and the display mode to use
38 :     ) = @_;
39 : sh002i 415
40 : sh002i 558 # install a local warn handler to collect warnings
41 :     my $warnings = "";
42 :     local $SIG{__WARN__} = sub { $warnings .= shift };
43 : sh002i 414
44 :     # create a Translator
45 : sh002i 558 #warn "PG: creating a Translator\n";
46 : sh002i 414 my $translator = WeBWorK::PG::Translator->new;
47 :    
48 : sh002i 424 # set the directory hash
49 : sh002i 558 #warn "PG: setting the directory hash\n";
50 : sh002i 414 $translator->rh_directories({
51 :     courseScriptsDirectory => $courseEnv->{webworkDirs}->{macros},
52 :     macroDirectory => $courseEnv->{courseDirs}->{macros},
53 :     templateDirectory => $courseEnv->{courseDirs}->{templates},
54 :     tempDirectory => $courseEnv->{courseDirs}->{html_temp},
55 :     });
56 :    
57 : sh002i 424 # evaluate modules and "extra packages"
58 : sh002i 558 #warn "PG: evaluating modules and \"extra packages\"\n";
59 : sh002i 424 my @modules = @{ $courseEnv->{pg}->{modules} };
60 : sh002i 476 foreach my $module_packages_ref (@modules) {
61 :     my ($module, @extra_packages) = @$module_packages_ref;
62 :     # the first item is the main package
63 :     $translator->evaluate_modules($module);
64 : sh002i 424 # the remaining items are "extra" packages
65 : sh002i 476 $translator->load_extra_packages(@extra_packages);
66 : sh002i 414 }
67 :    
68 : sh002i 424 # set the environment (from defineProblemEnvir)
69 : sh002i 558 #warn "PG: setting the environment (from defineProblemEnvir)\n";
70 : sh002i 555 my $envir = defineProblemEnvir(
71 : sh002i 502 $courseEnv,
72 :     $user,
73 :     $key,
74 :     $set,
75 :     $problem,
76 :     $psvn,
77 :     $formFields,
78 :     $translationOptions,
79 : sh002i 555 );
80 :     $translator->environment($envir);
81 : sh002i 414
82 : sh002i 424 # initialize the Translator
83 : sh002i 558 #warn "PG: initializing the Translator\n";
84 : sh002i 414 $translator->initialize();
85 :    
86 : sh002i 424 # load PG.pl and dangerousMacros.pl using unrestricted_load
87 : sh002i 425 # i'd like to change this at some point to have the same sort of interface to global.conf
88 :     # that the module loading does -- have a list of macros to load unrestrictedly.
89 : sh002i 558 #warn "PG: loading PG.pl and dangerousMacros.pl using unrestricted_load\n";
90 : sh002i 414 my $pg_pl = $courseEnv->{webworkDirs}->{macros} . "/PG.pl";
91 : sh002i 424 my $dangerousMacros_pl = $courseEnv->{webworkDirs}->{macros} . "/dangerousMacros.pl";
92 : sh002i 414 my $err = $translator->unrestricted_load($pg_pl);
93 :     warn "Error while loading $pg_pl: $err" if $err;
94 :     $err = $translator->unrestricted_load($dangerousMacros_pl);
95 :     warn "Error while loading $dangerousMacros_pl: $err" if $err;
96 :    
97 : sh002i 424 # set the opcode mask (using default values)
98 : sh002i 558 #warn "PG: setting the opcode mask (using default values)\n";
99 : sh002i 414 $translator->set_mask();
100 :    
101 : sh002i 424 # store the problem source
102 : sh002i 558 #warn "PG: storing the problem source\n";
103 : sh002i 492 my $sourceFile = $problem->source_file;
104 :     $sourceFile = $courseEnv->{courseDirs}->{templates}."/".$sourceFile
105 :     unless ($sourceFile =~ /^\//);
106 : sh002i 526 eval { $translator->source_string(readFile($sourceFile)) };
107 :     if ($@) {
108 :     # well, we couldn't get the problem source, for some reason.
109 :     return bless {
110 :     translator => $translator,
111 :     head_text => "",
112 :     body_text => <<EOF,
113 :     WeBWorK::Utils::readFile($sourceFile) says:
114 :     $@
115 :     EOF
116 :     answers => {},
117 :     result => {},
118 :     state => {},
119 :     errors => "Failed to read the problem source file.",
120 : sh002i 558 warnings => $warnings,
121 : sh002i 526 flags => {error_flag => 1},
122 :     }, $class;
123 :     }
124 : sh002i 414
125 :     # install a safety filter (&safetyFilter)
126 : sh002i 558 #warn "PG: installing a safety filter\n";
127 : sh002i 414 $translator->rf_safety_filter(\&safetyFilter);
128 :    
129 : sh002i 415 # translate the PG source into text
130 : sh002i 558 #warn "PG: translating the PG source into text\n";
131 : sh002i 415 $translator->translate();
132 :    
133 : sh002i 555 # after we're done translating, we may have to clean up after the translator.
134 :     # for example, 'images' mode uses a tempdir for dvipng's temp files. We have
135 :     # to remove it.
136 :     if ($translationOptions->{displayMode} eq 'images' && $envir->{dvipngTempDir}) {
137 : sh002i 558 rmtree($envir->{dvipngTempDir}, 0, 0);
138 : sh002i 555 }
139 :    
140 : sh002i 476 my ($result, $state); # we'll need these on the other side of the if block!
141 :     if ($translationOptions->{processAnswers}) {
142 :    
143 :     # process student answers
144 : sh002i 558 #warn "PG: processing student answers\n";
145 : sh002i 476 $translator->process_answers($formFields);
146 :    
147 :     # retrieve the problem state and give it to the translator
148 : sh002i 558 #warn "PG: retrieving the problem state and giving it to the translator\n";
149 : sh002i 476 $translator->rh_problem_state({
150 :     recorded_score => $problem->status,
151 :     num_of_correct_ans => $problem->num_correct,
152 :     num_of_incorrect_ans => $problem->num_incorrect,
153 :     });
154 :    
155 :     # determine an entry order -- the ANSWER_ENTRY_ORDER flag is built by
156 :     # the PG macro package (PG.pl)
157 : sh002i 558 #warn "PG: determining an entry order\n";
158 : sh002i 476 my @answerOrder =
159 :     $translator->rh_flags->{ANSWER_ENTRY_ORDER}
160 :     ? @{ $translator->rh_flags->{ANSWER_ENTRY_ORDER} }
161 :     : keys %{ $translator->rh_evaluated_answers };
162 :    
163 :     # install a grader -- use the one specified in the problem,
164 :     # or fall back on the default from the course environment.
165 :     # (two magic strings are accepted, to avoid having to
166 :     # reference code when it would be difficult.)
167 : sh002i 558 #warn "PG: installing a grader\n";
168 : sh002i 476 my $grader = $translator->rh_flags->{PROBLEM_GRADER_TO_USE}
169 :     || $courseEnv->{pg}->{options}->{grader};
170 :     $grader = $translator->rf_std_problem_grader
171 :     if $grader eq "std_problem_grader";
172 :     $grader = $translator->rf_avg_problem_grader
173 :     if $grader eq "avg_problem_grader";
174 :     die "Problem grader $grader is not a CODE reference."
175 :     unless ref $grader eq "CODE";
176 :     $translator->rf_problem_grader($grader);
177 :    
178 :     # grade the problem
179 : sh002i 558 #warn "PG: grading the problem\n";
180 : sh002i 476 ($result, $state) = $translator->grade_problem(
181 :     answers_submitted => $translationOptions->{processAnswers},
182 :     ANSWER_ENTRY_ORDER => \@answerOrder,
183 :     );
184 :    
185 :     }
186 : sh002i 415
187 : sh002i 424 # return an object which contains the translator and the results of
188 :     # the translation process. this is DIFFERENT from the "format expected
189 :     # by Webwork.pm (and I believe processProblem8, but check.)"
190 :     return bless {
191 :     translator => $translator,
192 :     head_text => ${ $translator->r_header },
193 :     body_text => ${ $translator->r_text },
194 :     answers => $translator->rh_evaluated_answers,
195 :     result => $result,
196 :     state => $state,
197 : sh002i 558 errors => $translator->errors,
198 :     warnings => $warnings,
199 : sh002i 424 flags => $translator->rh_flags,
200 :     }, $class;
201 : sh002i 414 }
202 :    
203 :     # -----
204 :    
205 : sh002i 424 sub defineProblemEnvir($$$$$$$) {
206 :     my (
207 :     $courseEnv,
208 :     $user,
209 :     $key,
210 :     $set,
211 :     $problem,
212 :     $psvn,
213 :     $formFields,
214 :     $options,
215 :     ) = @_;
216 : sh002i 414
217 :     my %envir;
218 :    
219 :     # PG environment variables
220 :     # from docs/pglanguage/pgreference/environmentvariables as of 06/25/2002
221 :     # any changes are noted by "ADDED:" or "REMOVED:"
222 :    
223 :     # Vital state information
224 : sh002i 476 # ADDED: displayHintsQ, displaySolutionsQ, refreshMath2img
225 : sh002i 414
226 :     $envir{psvn} = $psvn;
227 :     $envir{psvnNumber} = $envir{psvn};
228 :     $envir{probNum} = $problem->id;
229 :     $envir{questionNumber} = $envir{probNum};
230 :     $envir{fileName} = $problem->source_file;
231 :     $envir{probFileName} = $envir{fileName};
232 :     $envir{problemSeed} = $problem->problem_seed;
233 : sh002i 424 $envir{displayMode} = translateDisplayModeNames($options->{displayMode});
234 : sh002i 414 $envir{languageMode} = $envir{displayMode};
235 :     $envir{outputMode} = $envir{displayMode};
236 : sh002i 424 $envir{displayHintsQ} = $options->{hints};
237 :     $envir{displaySolutionsQ} = $options->{solutions};
238 : sh002i 434 $envir{refreshMath2img} = $options->{refreshMath2img};
239 : sh002i 414
240 :     # Problem Information
241 :     # ADDED: courseName
242 :    
243 :     $envir{openDate} = $set->open_date;
244 : sh002i 424 $envir{formattedOpenDate} = formatDateTime($envir{openDate});
245 : sh002i 414 $envir{dueDate} = $set->due_date;
246 : sh002i 424 $envir{formattedDueDate} = formatDateTime($envir{dueDate});
247 : sh002i 414 $envir{answerDate} = $set->answer_date;
248 : sh002i 424 $envir{formattedAnswerDate} = formatDateTime($envir{answerDate});
249 : sh002i 414 $envir{numOfAttempts} = $problem->num_correct + $problem->num_incorrect;
250 :     $envir{problemValue} = $problem->value;
251 : sh002i 424 $envir{sessionKey} = $key;
252 : sh002i 414 $envir{courseName} = $courseEnv->{courseName};
253 :    
254 :     # Student Information
255 :     # ADDED: studentID
256 :    
257 :     $envir{sectionName} = $user->section;
258 :     $envir{sectionNumber} = $envir{sectionName};
259 :     $envir{recitationName} = $user->recitation;
260 :     $envir{recitationNumber} = $envir{recitationName};
261 :     $envir{setNumber} = $set->id;
262 :     $envir{studentLogin} = $user->id;
263 :     $envir{studentName} = $user->first_name . " " . $user->last_name;
264 : sh002i 424 $envir{studentID} = $user->student_id;
265 : sh002i 414
266 :     # Answer Information
267 : sh002i 434 # REMOVED: refSubmittedAnswers
268 : sh002i 414
269 : sh002i 434 $envir{inputs_ref} = $formFields;
270 : sh002i 414
271 : sh002i 433 # External Programs
272 : sh002i 526 # ADDED: externalLaTeXPath, externalDvipngPath, externalMath2imgPath
273 : sh002i 434
274 : sh002i 433 $envir{externalTTHPath} = $courseEnv->{externalPrograms}->{tth};
275 : sh002i 526 $envir{externalLaTeXPath} = $courseEnv->{externalPrograms}->{latex};
276 :     $envir{externalDvipngPath} = $courseEnv->{externalPrograms}->{dvipng};
277 : sh002i 433 $envir{externalMath2imgPath} = $courseEnv->{externalPrograms}->{math2img};
278 : sh002i 414
279 :     # Directories and URLs
280 :     # REMOVED: courseName
281 : sh002i 526 # ADDED: dvipngTempDir
282 : sh002i 414
283 : sh002i 526
284 : sh002i 414 $envir{cgiDirectory} = undef;
285 :     $envir{cgiURL} = undef;
286 :     $envir{classDirectory} = undef;
287 : sh002i 424 $envir{courseScriptsDirectory} = $courseEnv->{webworkDirs}->{macros}."/";
288 :     $envir{htmlDirectory} = $courseEnv->{courseDirs}->{html}."/";
289 : sh002i 414 $envir{htmlURL} = $courseEnv->{courseURLs}->{html};
290 : sh002i 424 $envir{macroDirectory} = $courseEnv->{courseDirs}->{macros}."/";
291 :     $envir{templateDirectory} = $courseEnv->{courseDirs}->{templates}."/";
292 :     $envir{tempDirectory} = $courseEnv->{courseDirs}->{html_temp}."/";
293 : sh002i 414 $envir{tempURL} = $courseEnv->{courseURLs}->{html_temp};
294 :     $envir{scriptDirectory} = undef;
295 :     $envir{webworkDocsURL} = $courseEnv->{webworkURLs}->{docs};
296 : sh002i 555 $envir{dvipngTempDir} = $options->{displayMode} eq 'images'
297 : sh002i 558 ? tempdir("webwork-dvipng-XXXXXXXX", DIR => $envir{tempDirectory})
298 : sh002i 555 : undef;
299 : sh002i 414
300 : sh002i 433 # Default values for evaluating answers
301 : sh002i 425
302 : sh002i 433 my $ansEvalDefaults = $courseEnv->{pg}->{ansEvalDefaults};
303 :     $envir{$_} = $ansEvalDefaults->{$_} foreach (keys %$ansEvalDefaults);
304 :    
305 :     # Other things...
306 :    
307 : sh002i 425 $envir{PROBLEM_GRADER_TO_USE} = $courseEnv->{pg}->{options}->{grader};
308 :    
309 : sh002i 414 return \%envir;
310 :     }
311 :    
312 : sh002i 424 sub translateDisplayModeNames($) {
313 :     my $name = shift;
314 :     return {
315 : sh002i 476 tex => "TeX",
316 : sh002i 424 plainText => "HTML",
317 :     formattedText => "HTML_tth",
318 : sh002i 433 images => "HTML_img"
319 : sh002i 424 }->{$name};
320 :     }
321 :    
322 : sh002i 414 sub safetyFilter {
323 : sh002i 415 my $answer = shift; # accepts one answer and checks it
324 : sh002i 414 my $submittedAnswer = $answer;
325 :     $answer = '' unless defined $answer;
326 :     my ($errorno);
327 :     $answer =~ tr/\000-\037/ /;
328 :     # Return if answer field is empty
329 :     unless ($answer =~ /\S/) {
330 :     #$errorno = "<BR>No answer was submitted.";
331 :     $errorno = 0; ## don't report blank answer as error
332 :     return ($answer,$errorno);
333 :     }
334 :     # replace ^ with ** (for exponentiation)
335 :     # $answer =~ s/\^/**/g;
336 :     # Return if forbidden characters are found
337 :     unless ($answer =~ /^[a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\(\)]+$/ ) {
338 :     $answer =~ tr/a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\(\)/#/c;
339 :     $errorno = "<BR>There are forbidden characters in your answer: $submittedAnswer<BR>";
340 :     return ($answer,$errorno);
341 :     }
342 :     $errorno = 0;
343 :     return($answer, $errorno);
344 :     }
345 :    
346 :     1;
347 : sh002i 440
348 :     __END__
349 :    
350 :     =head1 SYNOPSIS
351 :    
352 :     $pg = WeBWorK::PG->new(
353 : sh002i 502 $courseEnv, # a WeBWorK::CourseEnvironment object
354 :     $user, # a WeBWorK::User object
355 : sh002i 440 $sessionKey,
356 : sh002i 502 $set, # a WeBWorK::Set object
357 :     $problem, # a WeBWorK::Problem object
358 :     $psvn,
359 :     $formFields # in &WeBWorK::Form::Vars format
360 : sh002i 440 { # translation options
361 :     displayMode => "images", # (plainText|formattedText|images)
362 :     showHints => 1, # (0|1)
363 :     showSolutions => 0, # (0|1)
364 :     refreshMath2img => 0, # (0|1)
365 :     processAnswers => 1, # (0|1)
366 :     },
367 :     );
368 :    
369 :     $translator = $pg->{translator}; # WeBWorK::PG::Translator
370 :     $body = $pg->{body_text}; # text string
371 :     $header = $pg->{head_text}; # text string
372 :     $answerHash = $pg->{answers}; # WeBWorK::PG::AnswerHash
373 :     $result = $pg->{result}; # hash reference
374 :     $state = $pg->{state}; # hash reference
375 :     $errors = $pg->{errors}; # text string
376 :     $warnings = $pg->{warnings}; # text string
377 :     $flags = $pg->{flags}; # hash reference
378 :    
379 :     =head1 DESCRIPTION
380 :    
381 :     WeBWorK::PG encapsulates the PG translation process, making multiple calls to
382 :     WeBWorK::PG::Translator. Much of the flexibility of the Translator is hidden,
383 :     instead making choices that are appropriate for the webwork-modperl system.
384 :    
385 :     =head1 CONSTRUCTION
386 :    
387 :     =over
388 :    
389 : sh002i 502 =item new (ENVIRONMENT, USER, KEY, SET, PROBLEM, PSVN, FIELDS, OPTIONS)
390 : sh002i 440
391 :     The C<new> method creates a translator, initializes it using the parameters
392 :     specified, translates a PG file, and processes answers. It returns a reference
393 :     to a blessed hash containing the results of the translation process.
394 :    
395 :     =back
396 :    
397 :     =head2 Parameters
398 :    
399 :     =over
400 :    
401 :     =item ENVIRONMENT
402 :    
403 :     a WeBWorK::CourseEnvironment object
404 :    
405 :     =item USER
406 :    
407 : sh002i 502 a WeBWorK::User object
408 : sh002i 440
409 :     =item KEY
410 :    
411 :     the session key of the current session
412 :    
413 :     =item SET
414 :    
415 : sh002i 502 a WeBWorK::Set object
416 : sh002i 440
417 :     =item PROBLEM
418 :    
419 : sh002i 526 a WeBWorK::Problem object. The contents of the source_file field can specify a
420 :     PG file either by absolute path or path relative to the "templates" directory.
421 :     I<The caller should remove taint from this value before passing!>
422 : sh002i 440
423 : sh002i 502 =item PSVN
424 :    
425 :     the problem set version number
426 :    
427 :     =item FIELDS
428 :    
429 :     a reference to a hash (as returned by &WeBWorK::Form::Vars) containing form
430 :     fields submitted by a problem processor. The translator will look for fields
431 :     like "AnSwEr[0-9]" containing submitted student answers.
432 :    
433 : sh002i 440 =item OPTIONS
434 :    
435 :     a reference to a hash containing the following data:
436 :    
437 :     =over
438 :    
439 :     =item displayMode
440 :    
441 :     one of "plainText", "formattedText", or "images"
442 :    
443 :     =item showHints
444 :    
445 :     boolean, render hints
446 :    
447 :     =item showSolutions
448 :    
449 :     boolean, render solutions
450 :    
451 :     =item refreshMath2img
452 :    
453 :     boolean, force images created by math2img (in "images" mode) to be recreated,
454 :     even if the PG source has not been updated.
455 :    
456 :     =item processAnswers
457 :    
458 :     boolean, call answer evaluators and graders
459 :    
460 :     =back
461 :    
462 :     =back
463 :    
464 :     =head2 RETURN VALUE
465 :    
466 :     The C<new> method returns a blessed hash reference containing the following
467 :     fields. More information can be found in the documentation for
468 :     WeBWorK::PG::Translator.
469 :    
470 :     =over
471 :    
472 :     =item translator
473 :    
474 :     The WeBWorK::PG::Translator object used to render the problem.
475 :    
476 :     =item head_text
477 :    
478 :     HTML code for the E<lt>headE<gt> block of an resulting web page. Used for
479 :     JavaScript features.
480 :    
481 :     =item body_text
482 :    
483 :     HTML code for the E<lt>bodyE<gt> block of an resulting web page.
484 :    
485 :     =item answers
486 :    
487 :     An C<AnswerHash> object containing submitted answers, and results of answer
488 :     evaluation.
489 :    
490 :     =item result
491 :    
492 :     A hash containing the results of grading the problem.
493 :    
494 :     =item state
495 :    
496 :     A hash containing the new problem state.
497 :    
498 :     =item errors
499 :    
500 :     A string containing any errors encountered while rendering the problem.
501 :    
502 :     =item warnings
503 :    
504 :     A string containing any warnings encountered while rendering the problem.
505 :    
506 :     =item flags
507 :    
508 :     A hash containing PG_flags (see the Translator docs).
509 :    
510 :     =back
511 :    
512 :     =head1 OPERATION
513 :    
514 :     WeBWorK::PG goes through the following operations when constructed:
515 :    
516 :     =over
517 :    
518 :     =item Get database information
519 :    
520 :     Retrieve information about the current user, set, and problem from the
521 :     database.
522 :    
523 :     =item Create a translator
524 :    
525 :     Instantiate a WeBWorK::PG::Translator object.
526 :    
527 :     =item Set the directory hash
528 :    
529 :     Set the translator's directory hash (courseScripts, macros, templates, and temp
530 :     directories) from the course environment.
531 :    
532 :     =item Evaluate PG modules
533 :    
534 :     Using the module list from the course environment (pg->modules), perform a
535 :     "use"-like operation to evaluate modules at runtime.
536 :    
537 :     =item Set the problem environment
538 :    
539 :     Use data from the user, set, and problem, as well as the course environemnt and
540 :     translation options, to set the problem environment.
541 :    
542 :     =item Initialize the translator
543 :    
544 :     Call &WeBWorK::PG::Translator::initialize. What more do you want?
545 :    
546 :     =item Load PG.pl and dangerousMacros.pl
547 :    
548 :     These macros must be loaded without opcode masking, so they are loaded here.
549 :    
550 :     =item Set the opcode mask
551 :    
552 :     Set the opcode mask to the default specified by WeBWorK::PG::Translator.
553 :    
554 :     =item Load the problem source
555 :    
556 :     Give the problem source to the translator.
557 :    
558 :     =item Install a safety filter
559 :    
560 :     The safety filter is used to preprocess student input before evaluation. The
561 :     default safety filter, &WeBWorK::PG::safetyFilter, is used.
562 :    
563 :     =item Translate the problem source
564 :    
565 :     Call &WeBWorK::PG::Translator::translate to render the problem source into the
566 :     format given by the display mode.
567 :    
568 :     =item Process student answers
569 :    
570 :     Use form field inputs to evaluate student answers.
571 :    
572 :     =item Load the problem state
573 :    
574 :     Use values from the database to initialize the problem state, so that the
575 :     grader will have a point of reference.
576 :    
577 :     =item Determine an entry order
578 :    
579 :     Use the ANSWER_ENTRY_ORDER flag to determine the order of answers in the
580 :     problem. This is important for problems with dependancies among parts.
581 :    
582 :     =item Install a grader
583 :    
584 :     Use the PROBLEM_GRADER_TO_USE flag, or a default from the course environment,
585 :     to install a grader.
586 :    
587 :     =item Grade the problem
588 :    
589 :     Use the selected grader to grade the problem.
590 :    
591 :     =back
592 :    
593 :     =head1 AUTHOR
594 :    
595 :     Written by Sam Hathaway, sh002i (at) math.rochester.edu.
596 :    
597 :     =cut

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