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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 526 use File::Temp qw(tempdir);
17 : sh002i 414 use WeBWorK::DB::Classlist;
18 :     use WeBWorK::DB::WW;
19 :     use WeBWorK::PG::Translator;
20 : sh002i 492 use WeBWorK::Problem;
21 : sh002i 455 use WeBWorK::Utils qw(readFile formatDateTime);
22 : sh002i 414
23 : sh002i 424 sub new($$$$$$$$) {
24 : sh002i 415 my $invocant = shift;
25 :     my $class = ref($invocant) || $invocant;
26 : sh002i 424 my (
27 :     $courseEnv,
28 : sh002i 502 $user,
29 : sh002i 424 $key,
30 : sh002i 502 $set,
31 :     $problem,
32 :     $psvn,
33 :     $formFields, # in CGI::Vars format
34 : sh002i 424 $translationOptions, # hashref containing options for the
35 :     # translator, such as whether to show
36 :     # hints and the display mode to use
37 :     ) = @_;
38 : sh002i 415
39 : sh002i 502 # # get database information
40 :     # my $classlist = WeBWorK::DB::Classlist->new($courseEnv);
41 :     # my $wwdb = WeBWorK::DB::WW->new($courseEnv);
42 :     # my $user = $classlist->getUser($userName);
43 :     # my $set = $wwdb->getSet($userName, $setName);
44 :     # my $psvn = $wwdb->getPSVN($userName, $setName);
45 :     #
46 :     # my $problem;
47 :     # if ($problemNumber =~ /^\d+$/) {
48 :     # $problem = $wwdb->getProblem($userName, $setName, $problemNumber);
49 :     # } else {
50 :     # # This is the fun part: if $problemNumber is NON-NUMERIC, the
51 :     # # user wants to specify a PG file directly. We manufacture a
52 :     # # Problem object using fake data and the specified source file.
53 :     # # This is potentially dangerous since an untrusted user is
54 :     # # allowed to specifiy an arbitrary file to be evaluated as PG.
55 :     # # A user of PG.pm MUST MAKE SURE that if $problemNumber is
56 :     # # supplied by an untrusted source (i.e. the Apache request),
57 :     # # it is numberic. A simple
58 :     # #
59 :     # # die unless $problemNumber =~ /^\d+$/;
60 :     # #
61 :     # # should suffice.
62 :     # $problem = WeBWorK::Problem->new(
63 :     # id => 0,
64 :     # set_id => $set->id,
65 :     # login_id => $user->id,
66 :     # source_file => $problemNumber,
67 :     # # the rest of Problem's fields are not needed
68 :     # );
69 :     # }
70 : sh002i 414
71 :     # create a Translator
72 : sh002i 424 warn "PG: creating a Translator\n";
73 : sh002i 414 my $translator = WeBWorK::PG::Translator->new;
74 :    
75 : sh002i 424 # set the directory hash
76 :     warn "PG: setting the directory hash\n";
77 : sh002i 414 $translator->rh_directories({
78 :     courseScriptsDirectory => $courseEnv->{webworkDirs}->{macros},
79 :     macroDirectory => $courseEnv->{courseDirs}->{macros},
80 :     templateDirectory => $courseEnv->{courseDirs}->{templates},
81 :     tempDirectory => $courseEnv->{courseDirs}->{html_temp},
82 :     });
83 :    
84 : sh002i 424 # evaluate modules and "extra packages"
85 :     warn "PG: evaluating modules and \"extra packages\"\n";
86 :     my @modules = @{ $courseEnv->{pg}->{modules} };
87 : sh002i 476 foreach my $module_packages_ref (@modules) {
88 :     my ($module, @extra_packages) = @$module_packages_ref;
89 :     # the first item is the main package
90 :     $translator->evaluate_modules($module);
91 : sh002i 424 # the remaining items are "extra" packages
92 : sh002i 476 $translator->load_extra_packages(@extra_packages);
93 : sh002i 414 }
94 :    
95 : sh002i 424 # set the environment (from defineProblemEnvir)
96 :     warn "PG: setting the environment (from defineProblemEnvir)\n";
97 :     $translator->environment(defineProblemEnvir(
98 : sh002i 502 $courseEnv,
99 :     $user,
100 :     $key,
101 :     $set,
102 :     $problem,
103 :     $psvn,
104 :     $formFields,
105 :     $translationOptions,
106 :     ));
107 : sh002i 414
108 : sh002i 424 # initialize the Translator
109 :     warn "PG: initializing the Translator\n";
110 : sh002i 414 $translator->initialize();
111 :    
112 : sh002i 424 # load PG.pl and dangerousMacros.pl using unrestricted_load
113 : sh002i 425 # i'd like to change this at some point to have the same sort of interface to global.conf
114 :     # that the module loading does -- have a list of macros to load unrestrictedly.
115 : sh002i 424 warn "PG: loading PG.pl and dangerousMacros.pl using unrestricted_load\n";
116 : sh002i 414 my $pg_pl = $courseEnv->{webworkDirs}->{macros} . "/PG.pl";
117 : sh002i 424 my $dangerousMacros_pl = $courseEnv->{webworkDirs}->{macros} . "/dangerousMacros.pl";
118 : sh002i 414 my $err = $translator->unrestricted_load($pg_pl);
119 :     warn "Error while loading $pg_pl: $err" if $err;
120 :     $err = $translator->unrestricted_load($dangerousMacros_pl);
121 :     warn "Error while loading $dangerousMacros_pl: $err" if $err;
122 :    
123 : sh002i 424 # set the opcode mask (using default values)
124 :     warn "PG: setting the opcode mask (using default values)\n";
125 : sh002i 414 $translator->set_mask();
126 :    
127 : sh002i 424 # store the problem source
128 :     warn "PG: storing the problem source\n";
129 : sh002i 492 my $sourceFile = $problem->source_file;
130 :     $sourceFile = $courseEnv->{courseDirs}->{templates}."/".$sourceFile
131 :     unless ($sourceFile =~ /^\//);
132 : sh002i 526 eval { $translator->source_string(readFile($sourceFile)) };
133 :     if ($@) {
134 :     # well, we couldn't get the problem source, for some reason.
135 :     return bless {
136 :     translator => $translator,
137 :     head_text => "",
138 :     body_text => <<EOF,
139 :     WeBWorK::Utils::readFile($sourceFile) says:
140 :     $@
141 :     EOF
142 :     answers => {},
143 :     result => {},
144 :     state => {},
145 :     errors => "Failed to read the problem source file.",
146 :     warnings => undef,
147 :     flags => {error_flag => 1},
148 :     }, $class;
149 :     }
150 : sh002i 414
151 :     # install a safety filter (&safetyFilter)
152 : sh002i 424 warn "PG: installing a safety filter\n";
153 : sh002i 414 $translator->rf_safety_filter(\&safetyFilter);
154 :    
155 : sh002i 415 # translate the PG source into text
156 : sh002i 424 warn "PG: translating the PG source into text\n";
157 : sh002i 415 $translator->translate();
158 :    
159 : sh002i 476 my ($result, $state); # we'll need these on the other side of the if block!
160 :     if ($translationOptions->{processAnswers}) {
161 :    
162 :     # process student answers
163 :     warn "PG: processing student answers\n";
164 :     $translator->process_answers($formFields);
165 :    
166 :     # retrieve the problem state and give it to the translator
167 :     warn "PG: retrieving the problem state and giving it to the translator\n";
168 :     $translator->rh_problem_state({
169 :     recorded_score => $problem->status,
170 :     num_of_correct_ans => $problem->num_correct,
171 :     num_of_incorrect_ans => $problem->num_incorrect,
172 :     });
173 :    
174 :     # determine an entry order -- the ANSWER_ENTRY_ORDER flag is built by
175 :     # the PG macro package (PG.pl)
176 :     warn "PG: determining an entry order\n";
177 :     my @answerOrder =
178 :     $translator->rh_flags->{ANSWER_ENTRY_ORDER}
179 :     ? @{ $translator->rh_flags->{ANSWER_ENTRY_ORDER} }
180 :     : keys %{ $translator->rh_evaluated_answers };
181 :    
182 :     # install a grader -- use the one specified in the problem,
183 :     # or fall back on the default from the course environment.
184 :     # (two magic strings are accepted, to avoid having to
185 :     # reference code when it would be difficult.)
186 :     warn "PG: installing a grader\n";
187 :     my $grader = $translator->rh_flags->{PROBLEM_GRADER_TO_USE}
188 :     || $courseEnv->{pg}->{options}->{grader};
189 :     $grader = $translator->rf_std_problem_grader
190 :     if $grader eq "std_problem_grader";
191 :     $grader = $translator->rf_avg_problem_grader
192 :     if $grader eq "avg_problem_grader";
193 :     die "Problem grader $grader is not a CODE reference."
194 :     unless ref $grader eq "CODE";
195 :     $translator->rf_problem_grader($grader);
196 :    
197 :     # grade the problem
198 :     warn "PG: grading the problem\n";
199 :     ($result, $state) = $translator->grade_problem(
200 :     answers_submitted => $translationOptions->{processAnswers},
201 :     ANSWER_ENTRY_ORDER => \@answerOrder,
202 :     );
203 :    
204 :     }
205 : sh002i 415
206 : sh002i 424 # return an object which contains the translator and the results of
207 :     # the translation process. this is DIFFERENT from the "format expected
208 :     # by Webwork.pm (and I believe processProblem8, but check.)"
209 :     return bless {
210 :     translator => $translator,
211 :     head_text => ${ $translator->r_header },
212 :     body_text => ${ $translator->r_text },
213 :     answers => $translator->rh_evaluated_answers,
214 :     result => $result,
215 :     state => $state,
216 :     errors => $translator->errors, # *** what is this doing?
217 :     warnings => undef, # *** gotta catch warnings eventually...
218 :     flags => $translator->rh_flags,
219 :     }, $class;
220 : sh002i 414 }
221 :    
222 :     # -----
223 :    
224 : sh002i 424 sub defineProblemEnvir($$$$$$$) {
225 :     my (
226 :     $courseEnv,
227 :     $user,
228 :     $key,
229 :     $set,
230 :     $problem,
231 :     $psvn,
232 :     $formFields,
233 :     $options,
234 :     ) = @_;
235 : sh002i 414
236 :     my %envir;
237 :    
238 :     # PG environment variables
239 :     # from docs/pglanguage/pgreference/environmentvariables as of 06/25/2002
240 :     # any changes are noted by "ADDED:" or "REMOVED:"
241 :    
242 :     # Vital state information
243 : sh002i 476 # ADDED: displayHintsQ, displaySolutionsQ, refreshMath2img
244 : sh002i 414
245 :     $envir{psvn} = $psvn;
246 :     $envir{psvnNumber} = $envir{psvn};
247 :     $envir{probNum} = $problem->id;
248 :     $envir{questionNumber} = $envir{probNum};
249 :     $envir{fileName} = $problem->source_file;
250 :     $envir{probFileName} = $envir{fileName};
251 :     $envir{problemSeed} = $problem->problem_seed;
252 : sh002i 424 $envir{displayMode} = translateDisplayModeNames($options->{displayMode});
253 : sh002i 414 $envir{languageMode} = $envir{displayMode};
254 :     $envir{outputMode} = $envir{displayMode};
255 : sh002i 424 $envir{displayHintsQ} = $options->{hints};
256 :     $envir{displaySolutionsQ} = $options->{solutions};
257 : sh002i 434 $envir{refreshMath2img} = $options->{refreshMath2img};
258 : sh002i 414
259 :     # Problem Information
260 :     # ADDED: courseName
261 :    
262 :     $envir{openDate} = $set->open_date;
263 : sh002i 424 $envir{formattedOpenDate} = formatDateTime($envir{openDate});
264 : sh002i 414 $envir{dueDate} = $set->due_date;
265 : sh002i 424 $envir{formattedDueDate} = formatDateTime($envir{dueDate});
266 : sh002i 414 $envir{answerDate} = $set->answer_date;
267 : sh002i 424 $envir{formattedAnswerDate} = formatDateTime($envir{answerDate});
268 : sh002i 414 $envir{numOfAttempts} = $problem->num_correct + $problem->num_incorrect;
269 :     $envir{problemValue} = $problem->value;
270 : sh002i 424 $envir{sessionKey} = $key;
271 : sh002i 414 $envir{courseName} = $courseEnv->{courseName};
272 :    
273 :     # Student Information
274 :     # ADDED: studentID
275 :    
276 :     $envir{sectionName} = $user->section;
277 :     $envir{sectionNumber} = $envir{sectionName};
278 :     $envir{recitationName} = $user->recitation;
279 :     $envir{recitationNumber} = $envir{recitationName};
280 :     $envir{setNumber} = $set->id;
281 :     $envir{studentLogin} = $user->id;
282 :     $envir{studentName} = $user->first_name . " " . $user->last_name;
283 : sh002i 424 $envir{studentID} = $user->student_id;
284 : sh002i 414
285 :     # Answer Information
286 : sh002i 434 # REMOVED: refSubmittedAnswers
287 : sh002i 414
288 : sh002i 434 $envir{inputs_ref} = $formFields;
289 : sh002i 414
290 : sh002i 433 # External Programs
291 : sh002i 526 # ADDED: externalLaTeXPath, externalDvipngPath, externalMath2imgPath
292 : sh002i 434
293 : sh002i 433 $envir{externalTTHPath} = $courseEnv->{externalPrograms}->{tth};
294 : sh002i 526 $envir{externalLaTeXPath} = $courseEnv->{externalPrograms}->{latex};
295 :     $envir{externalDvipngPath} = $courseEnv->{externalPrograms}->{dvipng};
296 : sh002i 433 $envir{externalMath2imgPath} = $courseEnv->{externalPrograms}->{math2img};
297 : sh002i 414
298 :     # Directories and URLs
299 :     # REMOVED: courseName
300 : sh002i 526 # ADDED: dvipngTempDir
301 : sh002i 414
302 : sh002i 526
303 : sh002i 414 $envir{cgiDirectory} = undef;
304 :     $envir{cgiURL} = undef;
305 :     $envir{classDirectory} = undef;
306 : sh002i 424 $envir{courseScriptsDirectory} = $courseEnv->{webworkDirs}->{macros}."/";
307 :     $envir{htmlDirectory} = $courseEnv->{courseDirs}->{html}."/";
308 : sh002i 414 $envir{htmlURL} = $courseEnv->{courseURLs}->{html};
309 : sh002i 424 $envir{macroDirectory} = $courseEnv->{courseDirs}->{macros}."/";
310 :     $envir{templateDirectory} = $courseEnv->{courseDirs}->{templates}."/";
311 :     $envir{tempDirectory} = $courseEnv->{courseDirs}->{html_temp}."/";
312 : sh002i 414 $envir{tempURL} = $courseEnv->{courseURLs}->{html_temp};
313 :     $envir{scriptDirectory} = undef;
314 :     $envir{webworkDocsURL} = $courseEnv->{webworkURLs}->{docs};
315 : sh002i 526 $envir{dvipngTempDir} = tempdir("webwork-dvipng-XXXXXXXX", TMPDIR => 1);
316 : sh002i 414
317 : sh002i 433 # Default values for evaluating answers
318 : sh002i 425
319 : sh002i 433 my $ansEvalDefaults = $courseEnv->{pg}->{ansEvalDefaults};
320 :     $envir{$_} = $ansEvalDefaults->{$_} foreach (keys %$ansEvalDefaults);
321 :    
322 :     # Other things...
323 :    
324 : sh002i 425 $envir{PROBLEM_GRADER_TO_USE} = $courseEnv->{pg}->{options}->{grader};
325 :    
326 : sh002i 414 return \%envir;
327 :     }
328 :    
329 : sh002i 424 sub translateDisplayModeNames($) {
330 :     my $name = shift;
331 :     return {
332 : sh002i 476 tex => "TeX",
333 : sh002i 424 plainText => "HTML",
334 :     formattedText => "HTML_tth",
335 : sh002i 433 images => "HTML_img"
336 : sh002i 424 }->{$name};
337 :     }
338 :    
339 : sh002i 414 sub safetyFilter {
340 : sh002i 415 my $answer = shift; # accepts one answer and checks it
341 : sh002i 414 my $submittedAnswer = $answer;
342 :     $answer = '' unless defined $answer;
343 :     my ($errorno);
344 :     $answer =~ tr/\000-\037/ /;
345 :     # Return if answer field is empty
346 :     unless ($answer =~ /\S/) {
347 :     #$errorno = "<BR>No answer was submitted.";
348 :     $errorno = 0; ## don't report blank answer as error
349 :     return ($answer,$errorno);
350 :     }
351 :     # replace ^ with ** (for exponentiation)
352 :     # $answer =~ s/\^/**/g;
353 :     # Return if forbidden characters are found
354 :     unless ($answer =~ /^[a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\(\)]+$/ ) {
355 :     $answer =~ tr/a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\(\)/#/c;
356 :     $errorno = "<BR>There are forbidden characters in your answer: $submittedAnswer<BR>";
357 :     return ($answer,$errorno);
358 :     }
359 :     $errorno = 0;
360 :     return($answer, $errorno);
361 :     }
362 :    
363 :     1;
364 : sh002i 440
365 :     __END__
366 :    
367 :     =head1 SYNOPSIS
368 :    
369 :     $pg = WeBWorK::PG->new(
370 : sh002i 502 $courseEnv, # a WeBWorK::CourseEnvironment object
371 :     $user, # a WeBWorK::User object
372 : sh002i 440 $sessionKey,
373 : sh002i 502 $set, # a WeBWorK::Set object
374 :     $problem, # a WeBWorK::Problem object
375 :     $psvn,
376 :     $formFields # in &WeBWorK::Form::Vars format
377 : sh002i 440 { # translation options
378 :     displayMode => "images", # (plainText|formattedText|images)
379 :     showHints => 1, # (0|1)
380 :     showSolutions => 0, # (0|1)
381 :     refreshMath2img => 0, # (0|1)
382 :     processAnswers => 1, # (0|1)
383 :     },
384 :     );
385 :    
386 :     $translator = $pg->{translator}; # WeBWorK::PG::Translator
387 :     $body = $pg->{body_text}; # text string
388 :     $header = $pg->{head_text}; # text string
389 :     $answerHash = $pg->{answers}; # WeBWorK::PG::AnswerHash
390 :     $result = $pg->{result}; # hash reference
391 :     $state = $pg->{state}; # hash reference
392 :     $errors = $pg->{errors}; # text string
393 :     $warnings = $pg->{warnings}; # text string
394 :     $flags = $pg->{flags}; # hash reference
395 :    
396 :     =head1 DESCRIPTION
397 :    
398 :     WeBWorK::PG encapsulates the PG translation process, making multiple calls to
399 :     WeBWorK::PG::Translator. Much of the flexibility of the Translator is hidden,
400 :     instead making choices that are appropriate for the webwork-modperl system.
401 :    
402 :     =head1 CONSTRUCTION
403 :    
404 :     =over
405 :    
406 : sh002i 502 =item new (ENVIRONMENT, USER, KEY, SET, PROBLEM, PSVN, FIELDS, OPTIONS)
407 : sh002i 440
408 :     The C<new> method creates a translator, initializes it using the parameters
409 :     specified, translates a PG file, and processes answers. It returns a reference
410 :     to a blessed hash containing the results of the translation process.
411 :    
412 :     =back
413 :    
414 :     =head2 Parameters
415 :    
416 :     =over
417 :    
418 :     =item ENVIRONMENT
419 :    
420 :     a WeBWorK::CourseEnvironment object
421 :    
422 :     =item USER
423 :    
424 : sh002i 502 a WeBWorK::User object
425 : sh002i 440
426 :     =item KEY
427 :    
428 :     the session key of the current session
429 :    
430 :     =item SET
431 :    
432 : sh002i 502 a WeBWorK::Set object
433 : sh002i 440
434 :     =item PROBLEM
435 :    
436 : sh002i 526 a WeBWorK::Problem object. The contents of the source_file field can specify a
437 :     PG file either by absolute path or path relative to the "templates" directory.
438 :     I<The caller should remove taint from this value before passing!>
439 : sh002i 440
440 : sh002i 502 =item PSVN
441 :    
442 :     the problem set version number
443 :    
444 :     =item FIELDS
445 :    
446 :     a reference to a hash (as returned by &WeBWorK::Form::Vars) containing form
447 :     fields submitted by a problem processor. The translator will look for fields
448 :     like "AnSwEr[0-9]" containing submitted student answers.
449 :    
450 : sh002i 440 =item OPTIONS
451 :    
452 :     a reference to a hash containing the following data:
453 :    
454 :     =over
455 :    
456 :     =item displayMode
457 :    
458 :     one of "plainText", "formattedText", or "images"
459 :    
460 :     =item showHints
461 :    
462 :     boolean, render hints
463 :    
464 :     =item showSolutions
465 :    
466 :     boolean, render solutions
467 :    
468 :     =item refreshMath2img
469 :    
470 :     boolean, force images created by math2img (in "images" mode) to be recreated,
471 :     even if the PG source has not been updated.
472 :    
473 :     =item processAnswers
474 :    
475 :     boolean, call answer evaluators and graders
476 :    
477 :     =back
478 :    
479 :     =back
480 :    
481 :     =head2 RETURN VALUE
482 :    
483 :     The C<new> method returns a blessed hash reference containing the following
484 :     fields. More information can be found in the documentation for
485 :     WeBWorK::PG::Translator.
486 :    
487 :     =over
488 :    
489 :     =item translator
490 :    
491 :     The WeBWorK::PG::Translator object used to render the problem.
492 :    
493 :     =item head_text
494 :    
495 :     HTML code for the E<lt>headE<gt> block of an resulting web page. Used for
496 :     JavaScript features.
497 :    
498 :     =item body_text
499 :    
500 :     HTML code for the E<lt>bodyE<gt> block of an resulting web page.
501 :    
502 :     =item answers
503 :    
504 :     An C<AnswerHash> object containing submitted answers, and results of answer
505 :     evaluation.
506 :    
507 :     =item result
508 :    
509 :     A hash containing the results of grading the problem.
510 :    
511 :     =item state
512 :    
513 :     A hash containing the new problem state.
514 :    
515 :     =item errors
516 :    
517 :     A string containing any errors encountered while rendering the problem.
518 :    
519 :     =item warnings
520 :    
521 :     A string containing any warnings encountered while rendering the problem.
522 :    
523 :     =item flags
524 :    
525 :     A hash containing PG_flags (see the Translator docs).
526 :    
527 :     =back
528 :    
529 :     =head1 OPERATION
530 :    
531 :     WeBWorK::PG goes through the following operations when constructed:
532 :    
533 :     =over
534 :    
535 :     =item Get database information
536 :    
537 :     Retrieve information about the current user, set, and problem from the
538 :     database.
539 :    
540 :     =item Create a translator
541 :    
542 :     Instantiate a WeBWorK::PG::Translator object.
543 :    
544 :     =item Set the directory hash
545 :    
546 :     Set the translator's directory hash (courseScripts, macros, templates, and temp
547 :     directories) from the course environment.
548 :    
549 :     =item Evaluate PG modules
550 :    
551 :     Using the module list from the course environment (pg->modules), perform a
552 :     "use"-like operation to evaluate modules at runtime.
553 :    
554 :     =item Set the problem environment
555 :    
556 :     Use data from the user, set, and problem, as well as the course environemnt and
557 :     translation options, to set the problem environment.
558 :    
559 :     =item Initialize the translator
560 :    
561 :     Call &WeBWorK::PG::Translator::initialize. What more do you want?
562 :    
563 :     =item Load PG.pl and dangerousMacros.pl
564 :    
565 :     These macros must be loaded without opcode masking, so they are loaded here.
566 :    
567 :     =item Set the opcode mask
568 :    
569 :     Set the opcode mask to the default specified by WeBWorK::PG::Translator.
570 :    
571 :     =item Load the problem source
572 :    
573 :     Give the problem source to the translator.
574 :    
575 :     =item Install a safety filter
576 :    
577 :     The safety filter is used to preprocess student input before evaluation. The
578 :     default safety filter, &WeBWorK::PG::safetyFilter, is used.
579 :    
580 :     =item Translate the problem source
581 :    
582 :     Call &WeBWorK::PG::Translator::translate to render the problem source into the
583 :     format given by the display mode.
584 :    
585 :     =item Process student answers
586 :    
587 :     Use form field inputs to evaluate student answers.
588 :    
589 :     =item Load the problem state
590 :    
591 :     Use values from the database to initialize the problem state, so that the
592 :     grader will have a point of reference.
593 :    
594 :     =item Determine an entry order
595 :    
596 :     Use the ANSWER_ENTRY_ORDER flag to determine the order of answers in the
597 :     problem. This is important for problems with dependancies among parts.
598 :    
599 :     =item Install a grader
600 :    
601 :     Use the PROBLEM_GRADER_TO_USE flag, or a default from the course environment,
602 :     to install a grader.
603 :    
604 :     =item Grade the problem
605 :    
606 :     Use the selected grader to grade the problem.
607 :    
608 :     =back
609 :    
610 :     =head1 AUTHOR
611 :    
612 :     Written by Sam Hathaway, sh002i (at) math.rochester.edu.
613 :    
614 :     =cut

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