texfilterdir = "filter/tex"; $CFG->algebrafilterdir = "filter/algebra"; $CFG->algebraimagedir = "filter/algebra"; error_reporting(E_ALL); $query = urldecode($_SERVER['QUERY_STRING']); if ($query) { $output = $query; $splitpos = strpos($query,'&')-8; $algebra = substr($query,8,$splitpos); $md5 = md5($algebra); if (strpos($query,'ShowDB') || strpos($query,'DeleteDB')) { $texcache = get_record("cache_filters","filter","algebra", "md5key", $md5); } if (strpos($query,'ShowDB')) { if ($texcache) { $output = "DB cache_filters entry for $algebra\n"; $output .= "id = $texcache->id\n"; $output .= "filter = $texcache->filter\n"; $output .= "version = $texcache->version\n"; $output .= "md5key = $texcache->md5key\n"; $output .= "rawtext = $texcache->rawtext\n"; $output .= "timemodified = $texcache->timemodified\n"; } else { $output = "DB cache_filters entry for $algebra not found\n"; } } if (strpos($query,'DeleteDB')) { if ($texcache) { $output = "Deleting DB cache_filters entry for $algebra\n"; $result = delete_records("cache_filters","id",$texcache->id); if ($result) { $result = 1; } else { $result = 0; } $output .= "Number of records deleted = $result\n"; } else { $output = "Could not delete DB cache_filters entry for $algebra\nbecause it could not be found.\n"; } } if (strpos($query,'TeXStage1')) { $output = algebra2tex($algebra); } if (strpos($query,'TeXStage2')) { $output = algebra2tex($algebra); $output = refineTeX($output); } if (strpos($query,'ShowImage')) { $output = algebra2tex($algebra); $output = refineTeX($output); tex2image($output); } else { outputText($output); } exit; } function algebra2tex($algebra) { Global $CFG; $algebra = str_replace('<','<',$algebra); $algebra = str_replace('>','>',$algebra); $algebra = str_replace('<>','#',$algebra); $algebra = str_replace('<=','%',$algebra); $algebra = str_replace('>=','!',$algebra); $algebra = preg_replace('!\r\n?!',' ',$algebra); if ( (PHP_OS == "WINNT") || (PHP_OS == "WIN32") || (PHP_OS == "Windows") ) { $algebra = "\"". str_replace('"','\"',$algebra) . "\""; $cmd = "cd $CFG->dirroot/$CFG->algebrafilterdir & algebra2tex.pl $algebra"; } else { $algebra = escapeshellarg($algebra); $cmd = "cd $CFG->dirroot/$CFG->algebrafilterdir; ./algebra2tex.pl $algebra"; } $texexp = `$cmd`; return $texexp; } function refineTeX($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); $texexp = str_replace('\mbox{logten}','\mbox{log}_{10}',$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); return $texexp; } function outputText($texexp) { header("Content-type: text/html"); echo "
  if ($texexp) {
    $texexp = str_replace('<','<',$texexp);
    $texexp = str_replace('>','>',$texexp);
    $texexp = str_replace('"','"',$texexp);
    echo "$texexp\n\n";
  } else {
    echo "No text output available\n\n";
  echo "
\n"; } function tex2image($texexp) { global $CFG; if ($texexp) { $texexp = '\Large ' . $texexp; $lifetime = 86400; $image = md5($texexp) . ".gif"; $filetype = 'image/gif'; if (!file_exists("$CFG->dataroot/$CFG->algebraimagedir")) { make_upload_directory($CFG->algebraimagedir); } $pathname = "$CFG->dataroot/$CFG->algebraimagedir/$image"; switch (PHP_OS) { case "Linux": system("$CFG->dirroot/$CFG->texfilterdir/mimetex.linux -e $pathname ". escapeshellarg($texexp) ); break; case "WINNT": case "WIN32": case "Windows": $texexp = str_replace('"','\"',$texexp); system("$CFG->dirroot/$CFG->texfilterdir/mimetex.exe -e $pathname \"$texexp\""); break; case "Darwin": system("$CFG->dirroot/$CFG->texfilterdir/mimetex.darwin -e $pathname ". escapeshellarg($texexp) ); break; } } if ($texexp && file_exists($pathname)) { $lastmodified = filemtime($pathname); header("Last-Modified: " . gmdate("D, d M Y H:i:s", $lastmodified) . " GMT"); header("Expires: " . gmdate("D, d M Y H:i:s", time() + $lifetime) . " GMT"); header("Cache-control: max_age = $lifetime"); // a day header("Pragma: "); header("Content-disposition: inline; filename=$image"); header("Content-length: ".filesize($pathname)); header("Content-type: $filetype"); readfile("$pathname"); } else { echo "Image not found!"; } } ?> Algebra Filter Debugger

Please enter an algebraic expression without any surrounding @@ into the text box below. (Click here for help.)

  1. First click on this button to see the cache_filters database entry for this expression.
  2. If the database entry looks corrupt, click on this button to delete it:
  3. Now click on this button . A preliminary translation into TeX will appear in the box below.
  4. Next click on this button . A more refined translation into TeX will appear in the box below.
  5. Finally click on this button to show a graphic image of the algebraic expression.

Debugging Help

First here is a brief overview on how the algebra filter works. It takes an algebra expression and first translates it into TeX. It first looks for the TeX translation in the Moodle database in the table cache_filters in the field rawtext. If not found, it passes the algebraic expression to the Perl script algebra2tex.pl, which also uses the Perl library AlgParser.pm. It then saves the TeX translation in the database for subsequent uses and passes the TeX to the mimetex executable to be converted to a gif image. Here are a few common things that can go wrong and some suggestions on how you might try to fix them.

  1. Something had gone wrong on a previous occasion when the filter tried to translate this expression. Then the database entry for that expression contains a bad TeX translation in the rawtext field (usually blank). You can fix this by clicking on "Delete DB Entry"
  2. The First Stage TeX Translation gives a "No text output available" message. If your server is running Windows, this may be due to the fact that you haven't installed Perl or didn't install it correctly. If your server is running some version of Unix (e.g. Linux), then this may be due to your Perl binary being installed in a nonstandard location. To fix this edit the first line of the algebra2tex.pl script. Another possible problem which may affect both Unix and Windows servers is that the web server doesn't have execute permission on the algebra2tex.pl script. In that case change permissions accordingly
  3. The Second Stage TeX Translation produces malformed TeX. This indicates a bug in the algebra filter. Post the original algebraic expression and the bad TeX translation in the Mathematics Tools forum in the Using Moodle course on moodle.org.
  4. The TeX to gif image conversion process does not work. If your server is running Unix, a likely cause is that the mimetex binary you are using is incompatible with your operating system. You can try compiling it from the C sources downloaded from http://www.forkosh.com/mimetex.zip, or looking for an appropriate binary at http://moodle.org/download/mimetex/. You may then also need to edit your moodle/filter/algebra/pix.php file to add

    to the list of operating systems in the switch (PHP_OS) statement. Windows users may have a problem properly unzipping mimetex.exe. Make sure that mimetex.exe is is PRECISELY 328192 bytes in size. If not, download fresh copy from http://moodle.org/download/mimetex/windows/mimetex.exe. Lastly check the execute permissions on your mimetex binary, as outlined in item 2 above.