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<?php// This file is part of Moodle - http://moodle.org///// Moodle is free software: you can redistribute it and/or modify// it under the terms of the GNU General Public License as published by// the Free Software Foundation, either version 3 of the License, or// (at your option) any later version.//// Moodle is distributed in the hope that it will be useful,// but WITHOUT ANY WARRANTY; without even the implied warranty of// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the// GNU General Public License for more details.//// You should have received a copy of the GNU General Public License// along with Moodle. If not, see <http://www.gnu.org/licenses/>.namespace filter_algebra;use core\context\system as context_system;use core\output\actions\popup_action;use core\url;use stdClass;/*** Moodle - Filter for converting simple calculator-type algebraic expressions to cached gif images** NOTE: This Moodle text filter converts algebraic expressions delimited* by either @@...@@ or by <algebra...>...</algebra> tags* first converts it to TeX using WeBWorK algebra parser Perl library* AlgParser.pm, part of the WeBWorK distribution obtained from* http://webhost.math.rochester.edu/downloadwebwork/* then converts the TeX to gif images using* mimetex.cgi obtained from http://www.forkosh.com/mimetex.html authored by* John Forkosh john@forkosh.com. The mimetex.cgi ELF binary compiled for Linux i386* as well as AlgParser.pm are included with this distribution.* Note that there may be patent restrictions on the production of gif images* in Canada and some parts of Western Europe and Japan until July 2004.* -------------------------------------------------------------------------* You will then need to edit your moodle/config.php to invoke mathml_filter.php* -------------------------------------------------------------------------** @package filter_algebra* @subpackage algebra* @copyright 2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu* Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later*/class text_filter extends \core_filters\text_filter {#[\Override]public function filter($text, array $options = []) {global $CFG, $DB;// Do a quick check using stripos to avoid unnecessary work.if (!preg_match('/<algebra/i', $text) && !strstr($text, '@@')) {return $text;}preg_match_all('/@(@@+)([^@])/', $text, $matches);for ($i = 0; $i < count($matches[0]); $i++) {$replacement = str_replace('@', '@', $matches[1][$i]) . $matches[2][$i];$text = str_replace($matches[0][$i], $replacement, $text);}// The following regular expression matches TeX expressions delimited by:// <algebra> some algebraic input expression </algebra>// or @@ some algebraic input expression @@.preg_match_all('/<algebra>(.+?)<\/algebra>|@@(.+?)@@/is', $text, $matches);for ($i = 0; $i < count($matches[0]); $i++) {$algebra = $matches[1][$i] . $matches[2][$i];// Look for some common false positives, and skip processing them.if ($algebra == 'PLUGINFILE' || $algebra == 'DRAFTFILE') {// Raw pluginfile URL.continue;}if (preg_match('/^ -\d+(,\d+)? \+\d+(,\d+)? $/', $algebra)) {// Part of a unified diff.continue;}$algebra = str_replace('<nolink>', '', $algebra);$algebra = str_replace('</nolink>', '', $algebra);$algebra = str_replace('<span class="nolink">', '', $algebra);$algebra = str_replace('</span>', '', $algebra);$align = "middle";if (preg_match('/^align=bottom /', $algebra)) {$align = "text-bottom";$algebra = preg_replace('/^align=bottom /', '', $algebra);} else if (preg_match('/^align=top /', $algebra)) {$align = "text-top";$algebra = preg_replace('/^align=top /', '', $algebra);}$md5 = md5($algebra);$filename = $md5 . ".gif";if (! $texcache = $DB->get_record("cache_filters", ["filter" => "algebra", "md5key" => $md5])) {$algebra = str_replace('<', '<', $algebra);$algebra = str_replace('>', '>', $algebra);$algebra = str_replace('<>', '#', $algebra);$algebra = str_replace('<=', '%', $algebra);$algebra = str_replace('>=', '!', $algebra);$algebra = preg_replace('/([=><%!#] *)-/', "\$1 zeroplace -", $algebra);$algebra = str_replace('delta', 'zdelta', $algebra);$algebra = str_replace('beta', 'bita', $algebra);$algebra = str_replace('theta', 'thita', $algebra);$algebra = str_replace('zeta', 'zita', $algebra);$algebra = str_replace('eta', 'xeta', $algebra);$algebra = str_replace('epsilon', 'zepslon', $algebra);$algebra = str_replace('upsilon', 'zupslon', $algebra);$algebra = preg_replace('!\r\n?!', ' ', $algebra);$algebra = escapeshellarg($algebra);if ((PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows")) {$cmd = "cd $CFG->dirroot\\filter\\algebra & algebra2tex.pl $algebra";} else {$cmd = "cd $CFG->dirroot/filter/algebra; ./algebra2tex.pl $algebra";}$texexp = `$cmd`;if (preg_match('/parsehilight/', $texexp)) {$text = str_replace($matches[0][$i], "<b>Syntax error:</b> " . $texexp, $text);} else if ($texexp) {$texexp = str_replace('zeroplace', '', $texexp);$texexp = str_replace('#', '\not= ', $texexp);$texexp = str_replace('%', '\leq ', $texexp);$texexp = str_replace('!', '\geq ', $texexp);$texexp = str_replace('\left{', '{', $texexp);$texexp = str_replace('\right}', '}', $texexp);$texexp = str_replace('\fun', ' ', $texexp);$texexp = str_replace('infty', '\infty', $texexp);$texexp = str_replace('alpha', '\alpha', $texexp);$texexp = str_replace('gamma', '\gamma', $texexp);$texexp = str_replace('iota', '\iota', $texexp);$texexp = str_replace('kappa', '\kappa', $texexp);$texexp = str_replace('lambda', '\lambda', $texexp);$texexp = str_replace('mu', '\mu', $texexp);$texexp = str_replace('nu', '\nu', $texexp);$texexp = str_replace('xi', '\xi', $texexp);$texexp = str_replace('rho', '\rho', $texexp);$texexp = str_replace('sigma', '\sigma', $texexp);$texexp = str_replace('tau', '\tau', $texexp);$texexp = str_replace('phi', '\phi', $texexp);$texexp = str_replace('chi', '\chi', $texexp);$texexp = str_replace('psi', '\psi', $texexp);$texexp = str_replace('omega', '\omega', $texexp);$texexp = str_replace('zdelta', '\delta', $texexp);$texexp = str_replace('bita', '\beta', $texexp);$texexp = str_replace('thita', '\theta', $texexp);$texexp = str_replace('zita', '\zeta', $texexp);$texexp = str_replace('xeta', '\eta', $texexp);$texexp = str_replace('zepslon', '\epsilon', $texexp);$texexp = str_replace('zupslon', '\upsilon', $texexp);$texexp = str_replace('\mbox{logten}', '\mbox{log}_{10}', $texexp);$texexp = str_replace('\mbox{acos}', '\mbox{cos}^{-1}', $texexp);$texexp = str_replace('\mbox{asin}', '\mbox{sin}^{-1}', $texexp);$texexp = str_replace('\mbox{atan}', '\mbox{tan}^{-1}', $texexp);$texexp = str_replace('\mbox{asec}', '\mbox{sec}^{-1}', $texexp);$texexp = str_replace('\mbox{acsc}', '\mbox{csc}^{-1}', $texexp);$texexp = str_replace('\mbox{acot}', '\mbox{cot}^{-1}', $texexp);$texexp = str_replace('\mbox{acosh}', '\mbox{cosh}^{-1}', $texexp);$texexp = str_replace('\mbox{asinh}', '\mbox{sinh}^{-1}', $texexp);$texexp = str_replace('\mbox{atanh}', '\mbox{tanh}^{-1}', $texexp);$texexp = str_replace('\mbox{asech}', '\mbox{sech}^{-1}', $texexp);$texexp = str_replace('\mbox{acsch}', '\mbox{csch}^{-1}', $texexp);$texexp = str_replace('\mbox{acoth}', '\mbox{coth}^{-1}', $texexp);$texexp = preg_replace('/\\\sqrt{(.+?),(.+?)}/s', '\sqrt[' . "\$2]{\$1}", $texexp);$texexp = preg_replace('/\\\mbox{abs}\\\left\((.+?)\\\right\)/s', "|\$1|", $texexp);$texexp = preg_replace('/\\\log\\\left\((.+?),(.+?)\\\right\)/s', '\log_{' . "\$2}\\left(\$1\\right)", $texexp);$texexp = preg_replace('/(\\\cos|\\\sin|\\\tan|\\\sec|\\\csc|\\\cot)([h]*)\\\left\((.+?),(.+?)\\\right\)/s',"\$1\$2^{" . "\$4}\\left(\$3\\right)",$texexp,);$texexp = preg_replace('/\\\int\\\left\((.+?),(.+?),(.+?)\\\right\)/s', '\int_' . "{\$2}^{\$3}\$1 ", $texexp);$texexp = preg_replace('/\\\int\\\left\((.+?d[a-z])\\\right\)/s', '\int ' . "\$1 ", $texexp);$texexp = preg_replace('/\\\lim\\\left\((.+?),(.+?),(.+?)\\\right\)/s', '\lim_' . "{\$2\\to \$3}\$1 ", $texexp);// Remove a forbidden keyword.$texexp = str_replace('\mbox', '', $texexp);$texcache = new stdClass();$texcache->filter = 'algebra';$texcache->version = 1;$texcache->md5key = $md5;$texcache->rawtext = $texexp;$texcache->timemodified = time();$DB->insert_record("cache_filters", $texcache, false);$text = str_replace($matches[0][$i], self::get_image_markup($filename, $texexp, 0, 0, $align), $text);} else {$text = str_replace($matches[0][$i], "<b>Undetermined error:</b> " . $matches[0][$i], $text);}} else {$text = str_replace($matches[0][$i], self::get_image_markup($filename, $texcache->rawtext), $text);}}return $text;}/*** Create image link.** @param string $imagefile name of file* @param string $tex TeX notation (html entities already decoded)* @param int $height O means automatic* @param int $width O means automatic* @param string $align* @return string HTML markup*/protected function get_image_markup(string $imagefile,string $tex = "",int $height = 0,int $width = 0,string $align = 'middle',): string {// Given the path to a picture file in a course, or a URL,// this function includes the picture in the page.global $CFG, $OUTPUT;$output = "";$style = 'style="border:0px; vertical-align:' . $align . ';';$title = '';if ($tex) {$tex = html_entity_decode($tex, ENT_QUOTES, 'UTF-8');$title = 'title="' . s($tex) . '"';}if ($height) {$style .= " height:{$height}px;";}if ($width) {$style .= " width:{$width}px;";}$style .= '"';$anchorcontents = '';if ($imagefile) {$anchorcontents .= "<img $title alt=\"" . s($tex) . "\" src=\"";if ($CFG->slasharguments) {// Use this method if possible for better caching.$anchorcontents .= "$CFG->wwwroot/filter/algebra/pix.php/$imagefile";} else {$anchorcontents .= "$CFG->wwwroot/filter/algebra/pix.php?file=$imagefile";}$anchorcontents .= "\" $style />";$imagefound = file_exists("$CFG->dataroot/filter/algebra/$imagefile");if (!$imagefound && has_capability('moodle/site:config', context_system::instance())) {$link = '/filter/algebra/algebradebug.php';$action = null;} else {$link = new url('/filter/tex/displaytex.php', ['texexp' => $tex]);// TODO: the popups do not work when text caching is enabled.$action = new popup_action('click', $link, 'popup', ['width' => 320, 'height' => 240]);}$output .= $OUTPUT->action_link($link, $anchorcontents, $action, ['title' => 'TeX']);} else {$output .= "Error: must pass URL or course";}return $output;}}