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1 : gage 1247 ################################################################################
2 :     # WeBWorK mod_perl (c) 2000-2002 WeBWorK Project
3 :     # $Id$
4 :     ################################################################################
5 :    
6 :     package WeBWorK::PG::Local;
7 :    
8 :     =head1 NAME
9 :    
10 :     WeBWorK::PG::Local - Use the WeBWorK::PG API to invoke a local
11 :     WeBWorK::PG::Translator object.
12 :    
13 :     =head1 DESCRIPTION
14 :    
15 :     WeBWorK::PG::Local encapsulates the PG translation process, making multiple
16 :     calls to WeBWorK::PG::Translator. Much of the flexibility of the Translator is
17 :     hidden, instead making choices that are appropriate for the webwork-modperl
18 :     system
19 :    
20 :     It implements the WeBWorK::PG interface and uses a local
21 :     WeBWorK::PG::Translator to perform problem rendering. See the documentation for
22 :     the WeBWorK::PG module for information about the API.
23 :    
24 :     =cut
25 :    
26 :     use strict;
27 :     use warnings;
28 :     use File::Path qw(rmtree);
29 :     use WeBWorK::PG::ImageGenerator;
30 :     use WeBWorK::PG::Translator;
31 :     use WeBWorK::Utils qw(readFile formatDateTime writeTimingLogEntry makeTempDirectory);
32 : gage 1249 BEGIN {
33 : gage 1247
34 : gage 1249 # This safe compartment is used to read the large macro files such as
35 :     # PG.pl, PGbasicmacros.pl and PGanswermacros and cache the results so that
36 :     # future calls have preloaded versions of these large files.
37 :     # This saves a significant amount of time.
38 :    
39 :     $WeBWorK::PG::Local::safeCache = new Safe;
40 :     # warn "Creating new Safe cache compartment ".$WeBWorK::PG::Local::safeCache->root;
41 :     }
42 : gage 1247 sub new {
43 :     my $invocant = shift;
44 :     my $class = ref($invocant) || $invocant;
45 :     my (
46 :     $ce,
47 :     $user,
48 :     $key,
49 :     $set,
50 :     $problem,
51 :     $psvn,
52 :     $formFields, # in CGI::Vars format
53 :     $translationOptions, # hashref containing options for the
54 :     # translator, such as whether to show
55 :     # hints and the display mode to use
56 :     ) = @_;
57 :    
58 :     # write timing log entry
59 :     writeTimingLogEntry($ce, "WeBWorK::PG::new",
60 :     "user=".$user->user_id.",problem=".$ce->{courseName}."/".$set->set_id."/".$problem->problem_id.",mode=".$translationOptions->{displayMode},
61 :     "begin");
62 :    
63 :     # install a local warn handler to collect warnings
64 :     my $warnings = "";
65 :     local $SIG{__WARN__} = sub { $warnings .= shift }
66 :     if $ce->{pg}->{options}->{catchWarnings};
67 :    
68 :     # create a Translator
69 : gage 1249 #warn "PG: creating a Translator\n";
70 : gage 1247 my $translator = WeBWorK::PG::Translator->new;
71 :    
72 :     # set the directory hash
73 :     #warn "PG: setting the directory hash\n";
74 :     $translator->rh_directories({
75 :     courseScriptsDirectory => $ce->{pg}->{directories}->{macros},
76 :     macroDirectory => $ce->{courseDirs}->{macros},
77 :     templateDirectory => $ce->{courseDirs}->{templates},
78 :     tempDirectory => $ce->{courseDirs}->{html_temp},
79 :     });
80 :    
81 :     # evaluate modules and "extra packages"
82 :     #warn "PG: evaluating modules and \"extra packages\"\n";
83 :     my @modules = @{ $ce->{pg}->{modules} };
84 :     foreach my $module_packages_ref (@modules) {
85 :     my ($module, @extra_packages) = @$module_packages_ref;
86 :     # the first item is the main package
87 :     $translator->evaluate_modules($module);
88 :     # the remaining items are "extra" packages
89 :     $translator->load_extra_packages(@extra_packages);
90 :     }
91 :    
92 :     # set the environment (from defineProblemEnvir)
93 :     #warn "PG: setting the environment (from defineProblemEnvir)\n";
94 :     my $envir = defineProblemEnvir(
95 :     $ce,
96 :     $user,
97 :     $key,
98 :     $set,
99 :     $problem,
100 :     $psvn,
101 :     $formFields,
102 :     $translationOptions,
103 :     );
104 :     $translator->environment($envir);
105 :    
106 :     # initialize the Translator
107 :     #warn "PG: initializing the Translator\n";
108 :     $translator->initialize();
109 : gage 1249 # $translator->dumpSafe; # debugging code
110 :     ###############################################################################
111 :     # Preload the macros files which are used routinely: PG.pl, dangerousMacros.pl, IO.pl
112 :     # PGbasicmacros.pl and PGanswermacros.pl
113 :     # Preloading the last two files safes a significant amount of time.
114 :     ###############################################################################
115 :    
116 :     # IO.pl, PG.pl, and dangerousMacros.pl are loaded using unrestricted_load
117 :     # This is hard wired into the Translator::pre_load_macro_files subroutine
118 :     # I'd like to change this at some point to have the same sort of interface to global.conf
119 : gage 1247 # that the module loading does -- have a list of macros to load unrestrictedly.
120 : gage 1249
121 :     # This has been replaced by the pre_load_macro_files subroutine. It loads AND caches the files.
122 :     # While PG.pl and dangerousMacros are not large, they are referred to by PGbasicmacros and PGanswermacros.
123 :     # Because these are loaded into the cached name space (e.g. Safe::Root1::) all calls to, say NEW_ANSWER_NAME
124 :     # are actually calls to Safe::Root1::NEW_ANSWER_NAME. It is useful to have these names inside the Safe::Root1:
125 :     # cached safe compartment. (NEW_ANSWER_NAME and all other subroutine names are also automatically exported into
126 :     # the current safe compartment Safe::Rootx::
127 :    
128 :     # The headers of both PGbasicmacros and PGanswermacros has code that insures that the constants used are imported into
129 :     # the current safe compartment. This involves evaluating references to, say $main::displayMode, at runtime to insure that main
130 :     # refers to Safe::Rootx:: and NOT to Safe::Root1::, which is the value of main:: at compile time.
131 :    
132 :    
133 :     ###############################################################################
134 : gage 1262 # TO ENABLE CACHEING UNCOMMENT THE CACHEING CODE
135 : gage 1249 # On webwork3 cached code is .2 seconds faster than non-cached code for an existing child.
136 :    
137 :     # CACHING CODE:
138 : gage 1306 eval{
139 : gage 1268 $translator->pre_load_macro_files($WeBWorK::PG::Local::safeCache, $ce->{pg}->{directories}->{macros},
140 : gage 1306 'PG.pl', 'dangerousMacros.pl','IO.pl','PGbasicmacros.pl','PGanswermacros.pl');};
141 :     warn "Error while preloading macro files: $@" if $@;
142 : gage 1249
143 : gage 1262 # STANDARD LOADING CODE: for cached script files this merely initializes the constants.
144 :     foreach (qw( PG.pl dangerousMacros.pl IO.pl)) {
145 : gage 1247 my $macroPath = $ce->{pg}->{directories}->{macros} . "/$_";
146 :     my $err = $translator->unrestricted_load($macroPath);
147 : gage 1249 warn "Error while loading $macroPath: |$err|" if $err;
148 : gage 1247 }
149 : gage 1249 ###############################################################################
150 :    
151 : gage 1247 # set the opcode mask (using default values)
152 :     #warn "PG: setting the opcode mask (using default values)\n";
153 :     $translator->set_mask();
154 :    
155 :     # store the problem source
156 :     #warn "PG: storing the problem source\n";
157 :     my $sourceFile = $problem->source_file;
158 :     $sourceFile = $ce->{courseDirs}->{templates}."/".$sourceFile
159 :     unless ($sourceFile =~ /^\//);
160 :     eval { $translator->source_string(readFile($sourceFile)) };
161 :     if ($@) {
162 :     # well, we couldn't get the problem source, for some reason.
163 :     return bless {
164 :     translator => $translator,
165 : gage 1249 head_text => "",
166 : gage 1247 body_text => <<EOF,
167 : gage 1249 WeBWorK::Utils::readFile($sourceFile) says:
168 : gage 1247 $@
169 :     EOF
170 :     answers => {},
171 :     result => {},
172 :     state => {},
173 :     errors => "Failed to read the problem source file.",
174 :     warnings => $warnings,
175 :     flags => {error_flag => 1},
176 :     }, $class;
177 :     }
178 :    
179 :     # install a safety filter (&safetyFilter)
180 :     #warn "PG: installing a safety filter\n";
181 :     $translator->rf_safety_filter(\&safetyFilter);
182 :    
183 :     # write timing log entry -- the translator is now all set up
184 :     writeTimingLogEntry($ce, "WeBWorK::PG::new",
185 :     "initialized",
186 :     "intermediate");
187 :    
188 :     # translate the PG source into text
189 :     #warn "PG: translating the PG source into text\n";
190 :     $translator->translate();
191 :    
192 :     # after we're done translating, we may have to clean up after the
193 :     # translator:
194 :    
195 :     # for example, HTML_img mode uses a tempdir for dvipng's temp files.\
196 :     # We have to remove it.
197 :     if ($envir->{dvipngTempDir}) {
198 :     rmtree($envir->{dvipngTempDir}, 0, 0);
199 :     }
200 :    
201 :     # HTML_dpng, on the other hand, uses an ImageGenerator. We have to
202 :     # render the queued equations.
203 :     if ($envir->{imagegen}) {
204 :     my $sourceFile = $ce->{courseDirs}->{templates} . "/" . $problem->source_file;
205 :     my %mtimeOption = -e $sourceFile
206 :     ? (mtime => (stat $sourceFile)[9])
207 :     : ();
208 :    
209 :     $envir->{imagegen}->render(
210 :     refresh => $translationOptions->{refreshMath2img},
211 :     %mtimeOption,
212 :     );
213 :     }
214 :    
215 :     my ($result, $state); # we'll need these on the other side of the if block!
216 :     if ($translationOptions->{processAnswers}) {
217 :    
218 :     # process student answers
219 :     #warn "PG: processing student answers\n";
220 :     $translator->process_answers($formFields);
221 :    
222 :     # retrieve the problem state and give it to the translator
223 :     #warn "PG: retrieving the problem state and giving it to the translator\n";
224 :     $translator->rh_problem_state({
225 :     recorded_score => $problem->status,
226 :     num_of_correct_ans => $problem->num_correct,
227 :     num_of_incorrect_ans => $problem->num_incorrect,
228 :     });
229 :    
230 :     # determine an entry order -- the ANSWER_ENTRY_ORDER flag is built by
231 :     # the PG macro package (PG.pl)
232 :     #warn "PG: determining an entry order\n";
233 :     my @answerOrder =
234 :     $translator->rh_flags->{ANSWER_ENTRY_ORDER}
235 :     ? @{ $translator->rh_flags->{ANSWER_ENTRY_ORDER} }
236 :     : keys %{ $translator->rh_evaluated_answers };
237 :    
238 :     # install a grader -- use the one specified in the problem,
239 :     # or fall back on the default from the course environment.
240 :     # (two magic strings are accepted, to avoid having to
241 :     # reference code when it would be difficult.)
242 :     #warn "PG: installing a grader\n";
243 :     my $grader = $translator->rh_flags->{PROBLEM_GRADER_TO_USE}
244 :     || $ce->{pg}->{options}->{grader};
245 :     $grader = $translator->rf_std_problem_grader
246 :     if $grader eq "std_problem_grader";
247 :     $grader = $translator->rf_avg_problem_grader
248 :     if $grader eq "avg_problem_grader";
249 :     die "Problem grader $grader is not a CODE reference."
250 :     unless ref $grader eq "CODE";
251 :     $translator->rf_problem_grader($grader);
252 :    
253 :     # grade the problem
254 :     #warn "PG: grading the problem\n";
255 :     ($result, $state) = $translator->grade_problem(
256 :     answers_submitted => $translationOptions->{processAnswers},
257 :     ANSWER_ENTRY_ORDER => \@answerOrder,
258 :     );
259 :    
260 :     }
261 :    
262 :     # write timing log entry
263 :     writeTimingLogEntry($ce, "WeBWorK::PG::new", "", "end");
264 :    
265 :     # return an object which contains the translator and the results of
266 :     # the translation process. this is DIFFERENT from the "format expected
267 :     # by Webwork.pm (and I believe processProblem8, but check.)"
268 :     return bless {
269 :     translator => $translator,
270 :     head_text => ${ $translator->r_header },
271 :     body_text => ${ $translator->r_text },
272 :     answers => $translator->rh_evaluated_answers,
273 :     result => $result,
274 :     state => $state,
275 :     errors => $translator->errors,
276 :     warnings => $warnings,
277 :     flags => $translator->rh_flags,
278 :     }, $class;
279 :     }
280 :    
281 :     # -----
282 :    
283 :     sub defineProblemEnvir {
284 :     my (
285 :     $ce,
286 :     $user,
287 :     $key,
288 :     $set,
289 :     $problem,
290 :     $psvn,
291 :     $formFields,
292 :     $options,
293 :     ) = @_;
294 :    
295 :     my %envir;
296 :    
297 :     # ----------------------------------------------------------------------
298 :    
299 :     # PG environment variables
300 :     # from docs/pglanguage/pgreference/environmentvariables as of 06/25/2002
301 :     # any changes are noted by "ADDED:" or "REMOVED:"
302 :    
303 :     # Vital state information
304 :     # ADDED: displayHintsQ, displaySolutionsQ, refreshMath2img,
305 :     # texDisposition
306 :    
307 :     $envir{psvn} = $set->psvn;
308 :     $envir{psvnNumber} = $envir{psvn};
309 :     $envir{probNum} = $problem->problem_id;
310 :     $envir{questionNumber} = $envir{probNum};
311 :     $envir{fileName} = $problem->source_file;
312 :     $envir{probFileName} = $envir{fileName};
313 :     $envir{problemSeed} = $problem->problem_seed;
314 :     $envir{displayMode} = translateDisplayModeNames($options->{displayMode});
315 :     $envir{languageMode} = $envir{displayMode};
316 :     $envir{outputMode} = $envir{displayMode};
317 :     $envir{displayHintsQ} = $options->{showHints};
318 :     $envir{displaySolutionsQ} = $options->{showSolutions};
319 :     # FIXME: this is HTML_img specific
320 :     #$envir{refreshMath2img} = $options->{refreshMath2img};
321 :     $envir{texDisposition} = "pdf"; # in webwork-modperl, we use pdflatex
322 :    
323 :     # Problem Information
324 :     # ADDED: courseName, formatedDueDate
325 :    
326 :     $envir{openDate} = $set->open_date;
327 :     $envir{formattedOpenDate} = formatDateTime($envir{openDate});
328 :     $envir{dueDate} = $set->due_date;
329 :     $envir{formattedDueDate} = formatDateTime($envir{dueDate});
330 :     $envir{formatedDueDate} = $envir{formattedDueDate}; # typo in many header files
331 :     $envir{answerDate} = $set->answer_date;
332 :     $envir{formattedAnswerDate} = formatDateTime($envir{answerDate});
333 :     $envir{numOfAttempts} = ($problem->num_correct || 0) + ($problem->num_incorrect || 0);
334 :     $envir{problemValue} = $problem->value;
335 :     $envir{sessionKey} = $key;
336 :     $envir{courseName} = $ce->{courseName};
337 :    
338 :     # Student Information
339 :     # ADDED: studentID
340 :    
341 :     $envir{sectionName} = $user->section;
342 :     $envir{sectionNumber} = $envir{sectionName};
343 :     $envir{recitationName} = $user->recitation;
344 :     $envir{recitationNumber} = $envir{recitationName};
345 :     $envir{setNumber} = $set->set_id;
346 :     $envir{studentLogin} = $user->user_id;
347 :     $envir{studentName} = $user->first_name . " " . $user->last_name;
348 :     $envir{studentID} = $user->student_id;
349 :    
350 :     # Answer Information
351 :     # REMOVED: refSubmittedAnswers
352 :    
353 :     $envir{inputs_ref} = $formFields;
354 :    
355 :     # External Programs
356 :     # ADDED: externalLaTeXPath, externalDvipngPath,
357 :     # externalGif2EpsPath, externalPng2EpsPath
358 :    
359 :     $envir{externalTTHPath} = $ce->{externalPrograms}->{tth};
360 :     $envir{externalLaTeXPath} = $ce->{externalPrograms}->{latex};
361 :     $envir{externalDvipngPath} = $ce->{externalPrograms}->{dvipng};
362 :     $envir{externalGif2EpsPath} = $ce->{externalPrograms}->{gif2eps};
363 :     $envir{externalPng2EpsPath} = $ce->{externalPrograms}->{png2eps};
364 :     $envir{externalGif2PngPath} = $ce->{externalPrograms}->{gif2png};
365 :    
366 :     # Directories and URLs
367 :     # REMOVED: courseName
368 :     # ADDED: dvipngTempDir
369 :    
370 :     $envir{cgiDirectory} = undef;
371 :     $envir{cgiURL} = undef;
372 :     $envir{classDirectory} = undef;
373 :     $envir{courseScriptsDirectory} = $ce->{pg}->{directories}->{macros}."/";
374 :     $envir{htmlDirectory} = $ce->{courseDirs}->{html}."/";
375 :     $envir{htmlURL} = $ce->{courseURLs}->{html}."/";
376 :     $envir{macroDirectory} = $ce->{courseDirs}->{macros}."/";
377 :     $envir{templateDirectory} = $ce->{courseDirs}->{templates}."/";
378 :     $envir{tempDirectory} = $ce->{courseDirs}->{html_temp}."/";
379 :     $envir{tempURL} = $ce->{courseURLs}->{html_temp}."/";
380 :     $envir{scriptDirectory} = undef;
381 :     $envir{webworkDocsURL} = $ce->{webworkURLs}->{docs}."/";
382 :     # FIXME: this is HTML_img mode-specific
383 :     #$envir{dvipngTempDir} = $options->{displayMode} eq 'images'
384 :     # ? makeTempDirectory($envir{tempDirectory}, "webwork-dvipng")
385 :     # : undef;
386 :    
387 :     # Information for sending mail
388 :    
389 :     $envir{mailSmtpServer} = $ce->{mail}->{smtpServer};
390 :     $envir{mailSmtpSender} = $ce->{mail}->{smtpSender};
391 :     $envir{ALLOW_MAIL_TO} = $ce->{mail}->{allowedRecipients};
392 :    
393 :     # Default values for evaluating answers
394 :    
395 :     my $ansEvalDefaults = $ce->{pg}->{ansEvalDefaults};
396 :     $envir{$_} = $ansEvalDefaults->{$_} foreach (keys %$ansEvalDefaults);
397 :    
398 :     # ----------------------------------------------------------------------
399 :    
400 :     my $basename = "equation-$envir{psvn}.$envir{probNum}";
401 :     $basename .= ".$envir{problemSeed}" if $envir{problemSeed};
402 :    
403 :     # Object for generating equation images
404 :     $envir{imagegen} = WeBWorK::PG::ImageGenerator->new(
405 :     tempDir => $ce->{webworkDirs}->{tmp}, # global temp dir
406 :     dir => $envir{tempDirectory},
407 :     url => $envir{tempURL},
408 :     basename => $basename,
409 :     latex => $envir{externalLaTeXPath},
410 :     dvipng => $envir{externalDvipngPath},
411 : sh002i 1515 useCache => 1,
412 :     cacheDir => $ce->{webworkDirs}->{equationCache},
413 :     cacheURL => $ce->{webworkURLs}->{equationCache},
414 :     cacheDB => $ce->{webworkFiles}->{equationCacheDB},
415 : gage 1247 );
416 :    
417 :     # Other things...
418 :     $envir{QUIZ_PREFIX} = $options->{QUIZ_PREFIX}; # used by quizzes
419 :     $envir{PROBLEM_GRADER_TO_USE} = $ce->{pg}->{options}->{grader};
420 :     $envir{PRINT_FILE_NAMES_FOR} = $ce->{pg}->{specialPGEnvironmentVars}->{PRINT_FILE_NAMES_FOR};
421 :    
422 :     # variables for interpreting capa problems.
423 :     $envir{CAPA_Tools} = $ce->{pg}->{specialPGEnvironmentVars}->{CAPA_Tools};
424 :     $envir{CAPA_MCTools} = $ce->{pg}->{specialPGEnvironmentVars}->{CAPA_MCTools};
425 :     $envir{CAPA_Graphics_URL} = $ce->{pg}->{specialPGEnvironmentVars}->{CAPA_Graphics_URL};
426 :     $envir{CAPA_GraphicsDirectory} = $ce->{pg}->{specialPGEnvironmentVars}->{CAPA_GraphicsDirectory};
427 :    
428 :     return \%envir;
429 :     }
430 :    
431 :     sub translateDisplayModeNames($) {
432 :     my $name = shift;
433 :     return {
434 :     tex => "TeX",
435 :     plainText => "HTML",
436 :     formattedText => "HTML_tth",
437 :     images => "HTML_dpng", # "HTML_img",
438 :     }->{$name};
439 :     }
440 :    
441 :     sub safetyFilter {
442 :     my $answer = shift; # accepts one answer and checks it
443 :     my $submittedAnswer = $answer;
444 :     $answer = '' unless defined $answer;
445 :     my ($errorno);
446 :     $answer =~ tr/\000-\037/ /;
447 :     # Return if answer field is empty
448 :     unless ($answer =~ /\S/) {
449 :     #$errorno = "<BR>No answer was submitted.";
450 :     $errorno = 0; ## don't report blank answer as error
451 :     return ($answer,$errorno);
452 :     }
453 :     # replace ^ with ** (for exponentiation)
454 :     # $answer =~ s/\^/**/g;
455 :     # Return if forbidden characters are found
456 :     unless ($answer =~ /^[a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\[\]\(\)\,\|]+$/ ) {
457 :     $answer =~ tr/a-zA-Z0-9_\-\+ \t\/@%\*\.\n^\(\)/#/c;
458 :     $errorno = "<BR>There are forbidden characters in your answer: $submittedAnswer<BR>";
459 :     return ($answer,$errorno);
460 :     }
461 :     $errorno = 0;
462 :     return($answer, $errorno);
463 :     }
464 :    
465 :     1;
466 :    
467 :     __END__
468 :    
469 :     =head1 OPERATION
470 :    
471 :     WeBWorK::PG goes through the following operations when constructed:
472 :    
473 :     =over
474 :    
475 :     =item Get database information
476 :    
477 :     Retrieve information about the current user, set, and problem from the
478 :     database.
479 :    
480 :     =item Create a translator
481 :    
482 :     Instantiate a WeBWorK::PG::Translator object.
483 :    
484 :     =item Set the directory hash
485 :    
486 :     Set the translator's directory hash (courseScripts, macros, templates, and temp
487 :     directories) from the course environment.
488 :    
489 :     =item Evaluate PG modules
490 :    
491 :     Using the module list from the course environment (pg->modules), perform a
492 :     "use"-like operation to evaluate modules at runtime.
493 :    
494 :     =item Set the problem environment
495 :    
496 :     Use data from the user, set, and problem, as well as the course environemnt and
497 :     translation options, to set the problem environment.
498 :    
499 :     =item Initialize the translator
500 :    
501 :     Call &WeBWorK::PG::Translator::initialize. What more do you want?
502 :    
503 :     =item Load PG.pl and dangerousMacros.pl
504 :    
505 :     These macros must be loaded without opcode masking, so they are loaded here.
506 :    
507 :     =item Set the opcode mask
508 :    
509 :     Set the opcode mask to the default specified by WeBWorK::PG::Translator.
510 :    
511 :     =item Load the problem source
512 :    
513 :     Give the problem source to the translator.
514 :    
515 :     =item Install a safety filter
516 :    
517 :     The safety filter is used to preprocess student input before evaluation. The
518 :     default safety filter, &WeBWorK::PG::safetyFilter, is used.
519 :    
520 :     =item Translate the problem source
521 :    
522 :     Call &WeBWorK::PG::Translator::translate to render the problem source into the
523 :     format given by the display mode.
524 :    
525 :     =item Process student answers
526 :    
527 :     Use form field inputs to evaluate student answers.
528 :    
529 :     =item Load the problem state
530 :    
531 :     Use values from the database to initialize the problem state, so that the
532 :     grader will have a point of reference.
533 :    
534 :     =item Determine an entry order
535 :    
536 :     Use the ANSWER_ENTRY_ORDER flag to determine the order of answers in the
537 :     problem. This is important for problems with dependancies among parts.
538 :    
539 :     =item Install a grader
540 :    
541 :     Use the PROBLEM_GRADER_TO_USE flag, or a default from the course environment,
542 :     to install a grader.
543 :    
544 :     =item Grade the problem
545 :    
546 :     Use the selected grader to grade the problem.
547 :    
548 :     =back
549 :    
550 :     =head1 AUTHOR
551 :    
552 :     Written by Sam Hathaway, sh002i (at) math.rochester.edu.
553 :    
554 :     =cut

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