--- loncom/xml/lontexconvert.pm	2001/05/03 22:54:12	1.2
+++ loncom/xml/lontexconvert.pm	2014/06/18 06:48:03	1.116
@@ -1,92 +1,725 @@
 # The LearningOnline Network with CAPA
 # TeX Conversion Module
 #
-# 05/29/00,05/30,10/11,10/20 Gerd Kortemeyer
-# 05/03/2001 Scott Harrison
+# $Id: lontexconvert.pm,v 1.116 2014/06/18 06:48:03 raeburn Exp $
+#
+# Copyright Michigan State University Board of Trustees
+#
+# This file is part of the LearningOnline Network with CAPA (LON-CAPA).
+#
+# LON-CAPA 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 2 of the License, or
+# (at your option) any later version.
+#
+# LON-CAPA 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 LON-CAPA; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# /home/httpd/html/adm/gpl.txt
+#
+# http://www.lon-capa.org/
+#
+# Copyright for TtHfunc and TtMfunc by Ian Hutchinson. 
+# TtHfunc and TtMfunc (the "Code") may be compiled and linked into 
+# binary executable programs or libraries distributed by the 
+# Michigan State University (the "Licensee"), but any binaries so 
+# distributed are hereby licensed only for use in the context
+# of a program or computational system for which the Licensee is the 
+# primary author or distributor, and which performs substantial 
+# additional tasks beyond the translation of (La)TeX into HTML.
+# The C source of the Code may not be distributed by the Licensee
+# to any other parties under any circumstances.
+#
 
 package Apache::lontexconvert;
 
 use strict;
-use tth;
+use tth();
 use vars qw($errorstring);
-use Apache::lonmsg;
+#use Apache::lonxml();
+use Apache::lonlocal;
+use Apache::lonnet;
+use lib '/home/httpd/lib/perl/';
+use LONCAPA;
+use URI::Escape;
+use IO::Socket::INET;
+
+
+#
+# Table of substitutions to unicode characters.
+#
+
+my %unicode_harpoons = (
+                        '\rightleftharpoons'  => 0x21cc,
+                      );
+
+my %unicode_translations = (
+
+# Brackets - unicode for browsers/OS which support it.
+
+    ''             => 0x23a1,
+    ''             => 0x23a2,
+    ''             => 0x23a3,
+    ''             => 0x23a4,
+    ''             => 0x23a5,
+    ''             => 0x23a6,
+
+#  Parens - unicode for browsers/OS which support it
+
+    ''              => 0x239b,
+    ''              => 0x239c,
+    ''              => 0x239d,
+    ''              => 0x239e,
+    ''              => 0x239f,
+    ''              => 0x23a0,
+
+);
+
+my %ascii_8bit_translations = (
+
+# Brackets - pure 8-bit ascii ugliness for browsers/OS which can't handle unicode
+
+    ''              => 0x5b,
+    ''              => 0x5b,    # '['
+    ''              => 0x5b,
+    ''              => 0x5d,    # ']'
+    ''              => 0x5d,
+    ''              => 0x5d,
+
+# Parens - pure 8-bit ascii ugliness for browsers/OS which can't handle unicode
+
+    ''              => 0x28,
+    ''              => 0x28,      # '('
+    ''              => 0x28,
+    ''              => 0x29,
+    ''              => 0x29,      # '('
+    ''              => 0x29,
+
+);
+
+##
+# Utility to convert elements of a string to unicode:
+#
+# @param input - Input string
+# @param pattern - Pattern to convert
+# @param unicode - Unicode to substitute for pattern.
+#
+# @return string - resulting string.
+# 
+sub unicode_subst {
+    my ($input, $pattern, $unicode) = @_;
+    
+    my $char = pack('U', $unicode);
+
+    $input =~ s/$pattern/$char/g;
+
+    return $input;
+}
 
 # ====================================================================== Header
 
-sub header {
-  $errorstring='';
-  my $time=time;
-  my $addhead=<<END;
-<script language="JavaScript">
-    if (window.location.pathname!="/res/adm/pages/menu.html") {
-	menu=window.open("","LONCAPAmenu");
-	menu.currentURL=window.location.pathname;
-    }
-</script>
-END
-  if ($ENV{'browser.mathml'}) {
-      &tth::ttminit();
-      return '<?xml version="1.0"?>'
-            .'<?xml-stylesheet type="text/css" href="/adm/MathML/mathml.css"?>'
-            .'<!DOCTYPE html SYSTEM "/adm/MathML/mathml.dtd" '
-            .'[<!ENTITY mathns "http://www.w3.org/1998/Math/MathML">]>'
-            .'<html xmlns:math="http://www.w3.org/1998/Math/MathML" ' 
-            .'xmlns="http://www.w3.org/TR/REC-html40">'
-	    ."<head>$addhead</head>"
-            ."\n";
-  } else {
-      &tth::tthinit();
-      my $headerstring='<html>';
-      if ($ENV{'browser.os'} eq 'mac') { 
-         $headerstring.="<head>\n"
-             .'<meta Content-Type="text/html; charset=x-mac-roman">'
-	     ."\n$addhead</head>\n";
-      }
-      else {
-	  $headerstring.="<head>$addhead</head>";
-      }
-      return $headerstring."\n";
-  }
+sub init_tth {
+    my $options=$env{'course.'.$env{'request.course.id'}.'.tthoptions'};
+    if ($options =~ /\S/) {
+	$options = ' '.$options;
+    } else {
+	undef($options);
+    }
+    if ($env{'browser.mathml'}) {
+	&tth::ttminit();
+	if ($env{'browser.unicode'}) {
+	    &tth::ttmoptions('-L -u1'.$options);
+	} else {
+	    &tth::ttmoptions('-L -u0'.$options);
+	}
+    } else {
+	&tth::tthinit();
+	if ($env{'browser.unicode'}) {
+	    &tth::tthoptions('-L -u1'.$options);
+	} else {
+	    &tth::tthoptions('-L -u0'.$options);
+	}
+    }
 }
 
 # ================================================================== Conversion
 
-sub converted {
+$Apache::lontexconvert::messedup=0;
+
+
+sub convert_real {
+    my ($texstring)=@_;
+    my ($xmlstring,$errorstring);
+    local $SIG{SEGV}=sub { $Apache::lontexconvert::messedup=1; die; };
+    local $SIG{ALRM}=sub { 
+	&Apache::lonnet::logthis("ALRM");
+	$xmlstring='['.&mt("TeX unconverted due to errors").']';
+	$Apache::lontexconvert::messedup=1;
+	die &mt("TeX unconverted due to errors");
+    };
+    &Apache::lonxml::start_alarm();
+    if ($env{'browser.mathml'}) {
+	$xmlstring=&tth::ttm($$texstring);
+	$xmlstring=~s/\<math\>/\<math xmlns=\"\&mathns\;\"\>/g;
+	$xmlstring=~s/\<br\>/\<br\/\>/g;
+	$xmlstring=~s/\<p\>/\<p\>\<\/p\>/g;
+	$errorstring.=&tth::ttmerror();
+    } else {
+	$xmlstring=&tth::tth($$texstring);
+	$errorstring.=&tth::ttherror();
+	$xmlstring=~s-</font(\s*)>-</font>-g;
+    }
+    $xmlstring=~s/^\s*\<br clear\=\"all\"/\<br/s;
+    $xmlstring=~s/^\s*//;
+    $xmlstring=~s/\s*$//;
+    &Apache::lonxml::end_alarm();
+
+    #
+    # Several strings produced by tth require
+    # transliteration -> unicode equivalents to render reliably
+    # in browsers. %unicode_translations and %unicode_harpoons are tables of
+    # string->substitution which we now apply. (%ascii_8bit_translations used
+    # instead for Windows XP and mobile devices.
+
+    my $use_ascii;
+    if ($env{'browser.os'} eq 'win') {
+        if (($env{'browser.osversion'}) && ($env{'browser.osversion'} < 6.0)) {
+            $use_ascii = 1;
+        }
+    }
+    if ($env{'browser.mobile'}) {
+        $use_ascii = 1;
+    }
+
+    foreach my $pattern (keys(%unicode_translations)) {
+	my $unicode = $unicode_translations{$pattern};
+	if ($use_ascii) {
+	    $unicode = $ascii_8bit_translations{$pattern};
+	}
+	$xmlstring = &unicode_subst($xmlstring, $pattern, $unicode);
+    }
+
+    foreach my $pattern (keys(%unicode_harpoons)) {
+        $xmlstring = &unicode_subst($xmlstring, $pattern, $unicode_harpoons{$pattern});
+    }
+
+    return ($xmlstring,$errorstring);
+}
+
+sub tth_converted {
+    my $texstring=shift;
+    my $xmlstring='['.&mt('UNDISPLAYABLE').']';
+    if ($Apache::lontexconvert::messedup) {
+	return '['.&mt('TeX unconverted due to previous errors').']';
+    }
+    $$texstring ='\\documentstyle{article}'.$$texstring;
+
+    eval(<<'ENDCONV');
+    ($xmlstring,$errorstring)=&convert_real($texstring)
+ENDCONV
+    if ($@) {
+	$errorstring.=&mt("Evaluation Error: ").$@;
+	$Apache::lontexconvert::messedup=1;
+    }
+    if ($Apache::lontexconvert::messedup || &tth::tthmessedup() || 
+	$errorstring) {
+	&Apache::lonnet::logthis("Trying to kill myself");
+	$Apache::lontexconvert::messedup=1;
+	if (ref($Apache::lonxml::request)) {
+	    $Apache::lonxml::request->child_terminate();
+	} else {
+	    my $request;
+	    eval { $request=Apache->request; };
+	    if (!$request) {
+		eval { $request=Apache2::RequestUtil->request; };
+	    }
+	    if ($request) {
+		$request->child_terminate();
+	    } else {
+		&Apache::lonnet::logthis("Unable to find a request to do child_terminate on");
+	    }
+	}
+    }
+    return $xmlstring;
+}
+
+sub clean_out_math_mode {
+    my ($texstring)=@_;
+    $$texstring=~s/(?<!\\)\$//g;
+    $$texstring=~s/\\[\)\(\]\[]//g;
+    $$texstring=~s/\\ensuremath//g;
+    return '';
+}
+
+sub displaystyle {
+    my ($texstring)=@_;
+    #has a $$ or \[ or \displaystyle or eqnarray in it, guessinng it's display mode
+    if ($$texstring=~/[^\\]\$\$/ ||
+        $$texstring=~/\\\[/ ||
+        $$texstring=~/\\displaystyle/ ||
+        $$texstring=~/eqnarray/
+       ) { return 1; }
+    return 0;
+}
+
+sub MathJax_converted {
+    my $texstring=shift;
+    my $tag='math/tex;';
+    if (&displaystyle($texstring)) { $tag='math/tex; mode=display'; }
+    &clean_out_math_mode($texstring);
+    return &MathJax_header().
+      '<script type="'.$tag.'">'.$$texstring.'</script>';
+}
+
+{
+    #Relies heavily on the previous jsMath installation
+    my @MathJax_sent_header;
+    sub MathJax_reset {
+        undef(@MathJax_sent_header);
+    }
+    sub MathJax_push {
+        push(@MathJax_sent_header,0);
+    }
+    sub MathJax_header {
+        if (!@MathJax_sent_header) {
+            &Apache::lonnet::logthis("mismatched calls of MathJax_header and MathJax_process");
+            return '';
+        }
+        return '' if $MathJax_sent_header[-1];
+        $MathJax_sent_header[-1]=1;
+        return
+          '<script type="text/javascript" src="/adm/MathJax/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>'."\n";
+    }
+    #sub MathJax_process {
+    #    my $state = pop(@MathJax_sent_header);
+    #    return '' if !$state;
+    #    return "\n".
+    #        '<script type="text/javascript">MathJax.Process()</script>'."\n";
+    #}
+    #sub MathJax_state {
+    #    my ($level) = @_;
+    #    return $MathJax_sent_header[$level];
+    #}
+}
+
+
+sub jsMath_converted {
+    my $texstring=shift;
+    my $tag='span';
+    if (&displaystyle($texstring)) { $tag='div'; }
+    &clean_out_math_mode($texstring);
+    return &jsMath_header().
+	'<'.$tag.' class="math">'.$$texstring.'</'.$tag.'>';
+}
+
+{
+    my @jsMath_sent_header;
+    sub jsMath_reset {
+	undef(@jsMath_sent_header);
+    }
+    sub jsMath_push {
+	push(@jsMath_sent_header,0);
+    }
+    sub jsMath_header {
+	if (!@jsMath_sent_header) {
+	    &Apache::lonnet::logthis("mismatched calls of jsMath_header and jsMath_process");
+	    return '';
+	}
+	return '' if $jsMath_sent_header[-1];
+	$jsMath_sent_header[-1]=1;
+	return
+            '<script type="text/javascript">
+                     function NoFontMessage () {}
+                     jsMath = {Parser: {prototype: {environments: {\'eqnarray*\' :[\'Array\',null,null,\'rcl\',[5/18,5/18],3,\'D\']}}}};
+                   </script>'."\n".
+	    '<script type="text/javascript" src="/adm/jsMath/jsMath.js"></script>'."\n";
+    }
+    sub jsMath_process {
+	my $state = pop(@jsMath_sent_header);
+	return '' if !$state;
+	return "\n".
+	    '<script type="text/javascript">jsMath.Process()</script>'."\n";
+    }
+    sub jsMath_state {
+	my ($level) = @_;
+	return $jsMath_sent_header[$level];
+    }
+}
+
+sub tex_engine {
+    if (exists($env{'form.texengine'})) {
+	if ($env{'form.texengine'} ne '') {
+            return $env{'form.texengine'};
+        }
+    }    
+    if ($env{'request.course.id'}
+	&& exists($env{'course.'.$env{'request.course.id'}.'.texengine'})) {
+	return $env{'course.'.$env{'request.course.id'}.'.texengine'};
+    }
+    if (exists($env{'environment.texengine'})) {
+	return $env{'environment.texengine'};
+    }
+    return 'tth';
+}
+
+sub init_math_support {
+    my ($inherit_jsmath) = @_;
+    &init_tth();
+    &Apache::lontexconvert::jsMath_push();
+    if (lc(&tex_engine()) eq 'jsmath' ||
+	($inherit_jsmath && &jsMath_state(-2))) {
+	return &Apache::lontexconvert::jsMath_header();
+    }
+    &Apache::lontexconvert::MathJax_push();
+    if (lc(&tex_engine()) eq 'mathjax') { # ||
+        #($inherit_jsmath && &jsMath_state(-2))) {
+        return &Apache::lontexconvert::MathJax_header();
+    }
+    return;
+}
+
+sub mimetex_valign {
+    my ($esc_texstring)=@_;
+    my $valign = 0;
+    my $path = '/cgi-bin/mimetex.cgi?'.$esc_texstring;
+    my $socket;
+    &Apache::lonxml::start_alarm();
+    $socket = IO::Socket::INET->new(PeerAddr => 'localhost',
+                                    PeerPort => 'http(80)',
+                                    Proto    => 'tcp');
+    if ($socket) {
+        my $headreq = "HEAD $path HTTP/1.0\r\n\r\n";
+        print $socket $headreq;
+        while (<$socket>) {
+            if (/Vertical\-Align\:\s*?([\-\d]+)/) {
+                $valign = $1;
+            }
+        }
+        $socket->close();
+    }
+    &Apache::lonxml::end_alarm();
+    return $valign;
+}
+
+sub mimetex_converted {
     my $texstring=shift;
-    my $xmlstring;
-    if ($ENV{'browser.mathml'}) {
-      $xmlstring=&tth::ttm($$texstring);
-      $xmlstring=~s/\<math\>/\<math xmlns=\"\&mathns\;\"\>/g;
-      $xmlstring=~s/\<br\>/\<br\/\>/g;
-      $xmlstring=~s/\<p\>/\<p\>\<\/p\>/g;
-      $errorstring.=&tth::ttmerror();
-  } else {
-      $xmlstring=&tth::tth($$texstring);
-      $errorstring.=&tth::ttherror();
-  }
-  return $xmlstring;
-}
-
-# ====================================================================== Footer
-
-sub footer {
-  my $xmlstring='';
-  if ($ENV{'request.state'} eq 'construct') {
-      $xmlstring.='<address>'.$errorstring.'</address>';
-  } else {
-      &Apache::lonmsg::author_res_msg($ENV{'request.filename'},$errorstring);
-  }
-# -------------------------------------------------------------------- End Body
-  $xmlstring.='</html>';
-  return $xmlstring;
+
+# Alt-Argument for screen readers
+    my $alt_string=$$texstring;
+    $alt_string=~s/\"/\'\'/g;
+
+# Is this displaystyle?
+
+    my $displaystyle=&displaystyle($texstring);
+
+# Remove math environment delimiters
+
+    &clean_out_math_mode($texstring);
+
+    if ($displaystyle) {
+	$$texstring='\\displaystyle \\Large '.$$texstring;
+    }
+    my $esc_texstring = &uri_escape($$texstring);
+    my $valign = &mimetex_valign($esc_texstring);
+    my $result='<img src="/cgi-bin/mimetex.cgi?'.$esc_texstring.'" style="vertical-align:'.$valign.'px" alt="'.$alt_string.'" />';
+    if ($displaystyle) {
+	$result='<div style="text-align:center">'.$result.'</div>';
+    }
+    return $result;
+}
+
+sub converted {
+    my ($string,$mode)=@_;
+    if ($mode eq '') { $mode = &tex_engine(); }
+    if ($mode =~ /tth/i) {
+	return &tth_converted($string);
+    } elsif ($mode =~ /jsmath/i) {
+	return &jsMath_converted($string);
+    } elsif ($mode =~ /mathjax/i) {
+	return &MathJax_converted($string);
+    } elsif ($mode =~ /mimetex/i) {
+	return &mimetex_converted($string);
+    } elsif ($mode =~ /raw/i) {
+        return $$string;
+    }
+    return &tth_converted($string);
+}
+
+# ------------------------------------------------------------ Message display
+
+sub to_convert {
+    my ($string) = @_;
+    &init_tth();
+    $string=~s/\<br\s*\/?\>/ /gs;
+#    $string=~s/\s/ /gs;
+    $string=&HTML::Entities::decode($string);
+    return &converted(\$string);
 }
 
+sub smiley {
+    my $expression=shift;
+    my %smileys=(
+    	 '\:\-*\)' => 'face-smile.png',
+		 '8\-\)'  => 'face-cool.png',
+		 '8\-(I|\|)'   => 'face-glasses.png',
+		 '\:\-(I|\|)'   => 'face-plain.png',
+		 '\:\-(o|O|\(\))' => 'face-surprise.png',
+		 ':\-\('  => 'face-sad.png',
+		 '\;\-\)' => 'face-wink.png',
+		 '\:\-(P|p)'  => 'face-raspberry.png',
+		 '\:\-(\\\|\\/)' => 'face-uncertain.png',
+		 '\:\-D'  => 'face-smile-big.png',
+		 '\:\-(C|\@)'  => 'face-angry.png',
+		 '\:(\'|\`)\-*\(' => 'face-crying.png',
+		 '\:\-(X|x|\#)' => 'face-quiet.png',
+		 '\:\-(s|S)' => 'face-uncertain.png',
+		 '\:\-\$' => 'face-embarrassed.png',
+		 '\:\-\*' => 'face-kiss.png',
+		 '\+O\(' => 'face-sick.png',
+		 '(\&lt\;3|\(heart\))' => 'heart.png',
+		 '\(rose\)' => 'rose.png',
+		 '\(pizza\)' => 'food-pizza.png',
+		 '\(cake\)' => 'food-cake.png',
+		 '\(ninja\)' => 'face-ninja.png',
+		 '\(pirate\)' => 'face-pirate.png',
+		 '\((agree|yes)\)' => 'opinion-agree.png',
+		 '\((disagree|nay)\)' => 'opinion-disagree.png',
+		 '(o|O)\-\)' => 'face-angel.png',
+		 );
+    my $iconpath=$Apache::lonnet::perlvar{'lonIconsURL'};
+    foreach my $smiley (keys(%smileys)) {
+	$expression=~s/$smiley/\<img src="$iconpath\/$smileys{$smiley}" \/\>/gs; 
+    }
+    return $expression;
+}
+
+sub msgtexconverted {
+    my ($message,$email) = @_;
+    $errorstring='';
+    my $outmessage='';
+    my $tex=0;
+    foreach my $fragment (split(/(?:\&lt\;|\<)\/*m\s*(?:\&gt\;|\>)/i,$message)) {
+	if ($tex) {
+	    if ($email) {
+		$outmessage.='</pre><tt>'.&to_convert($fragment).'</tt><pre>';
+		$tex=0;
+	    } else {
+		$outmessage.=&to_convert($fragment);
+		$tex=0;
+	    }
+	} else {
+            $outmessage.=&smiley($fragment);
+	    $tex=1;
+	}
+    }
+    $message=$outmessage; $outmessage=''; $tex=0;
+    foreach my $fragment (split(/(?:\&lt\;|\<)\/*algebra\s*(?:\&gt\;|\>)/i,
+				$message)) {
+	if ($tex) {
+        my $algebra = &algebra($fragment, 'web', undef, undef, undef, 'tth');
+	    if ($email) {
+		$outmessage.='</pre><tt>'.$algebra.'</tt><pre>';
+		$tex=0;
+	    } else {
+		$outmessage.=$algebra;
+		$tex=0;
+	    }
+	} else {
+        $outmessage.=$fragment;
+	    $tex=1;
+	}
+    }
+    if (wantarray) {
+	return ($outmessage,$errorstring);
+    } else {
+	return $outmessage.$errorstring;
+    }
+}
+
+sub algebra {
+    use AlgParser;
+    my ($string,$target,$style,$parstack,$safeeval,$tth)=@_;
+    my $parser = new AlgParserWithImplicitExpand;
+    if ($tth eq 'tth') {&init_tth();}
+    $string=&prepare_algebra($string);
+    my $ret = $parser->parse($string);
+    my $result='['.&mt('Algebra unconverted due to previous errors').']';
+    if ( ref($ret) ) {
+	#$parser->tostring();
+	$parser->normalize();
+	my $latex=$parser->tolatex();
+	$latex=&postprocess_algebra($latex);
+	if ($style eq 'display') {
+	    $latex='$$'.$latex.'$$x';
+	} else {
+	    # style is 'inline'
+	    $latex='\\ensuremath{'.$latex.'}';
+	}
+	if ($target eq 'web' || $target eq 'analyze') {
+            my $display=&Apache::lonxml::get_param('display',$parstack,$safeeval);
+            $result = &converted(\$latex,$display);
+#	    $result = &converted(\$latex);
+	} else {
+	    $result = $latex;
+	}
+    } else {
+	&Apache::lonxml::error($parser->{'htmlerror'});
+    }
+}
+
+sub prepare_algebra {
+    my ($string)=@_;
+
+    # makes the decision about what is a minus sign easier supposedly
+    $string =~ s/(\<\>|\<\=|\>\=[\=\>\<] *)-/$1 zeroplace -/g;
+
+    return $string;
+}
+
+sub postprocess_algebra {
+    my ($string)=@_;
+    
+    # moodle had these and I don't know why, ignoring them for now
+    # $string =~s/\\fun/ /g;
+
+    # sqrt(3,4) means the 4 root of 3
+    $string =~s/\\sqrt{([^,]+),([^\}]+)}/\\sqrt[$2]{$1}/gs;
+
+    # log(3,4) means the log base 4 of 3
+    $string =~s/\\log\\left\((.+?),(.+?)\\right\)/\\log_{$2}\\left($1\\right)/gs;
+
+    # log(3,4) means the log base 4 of 3
+    $string =~s/\\((?:sin|cos|tan|sec|csc|cot)(?:h)?)\\left\((.+?),(.+?)\\right\)/\\$1^{$3}\\left($2\\right)/gs;
+
+    # int(3,a,b) integral from a to b of 3
+    $string =~s/\\int\\left\((.+?),(.+?),(.+?)\\right\)/\\int_{$2}^{$3}\\left($1\\right)/gs;
+
+    # int( ... dx) -> ...
+    $string =~s/\\int\\left\((.+?)d[a-z]\\right\)/$1/gs;
+
+    # 
+    $string =~s/\\lim\\left\((.+?),(.+?),(.+?)\\right\)/\\lim_{$2\\to $3}$1/gs;
+    return $string;
+}
+
+
 1;
 __END__
 
 
+=pod
+
+=head1 NAME
+
+Apache::lontexconvert;
+
+=head1 SYNOPSIS
+
+Access to tth/ttm
+
+This is part of the LearningOnline Network with CAPA project
+described at http://www.lon-capa.org.
+
+
+=head1 SUBROUTINES
+
+=over
+
+=item init_tth()
+
+Header
+
+=item convert_real()
+
+ we need this routine because &converted can get called from inside
+ of the safespace (through &xmlparse('<m>stuff</m>') which doesn't
+ allow the opcode for alarm, so we need to compile this before we get
+ into the safe space since opcode checks only occur at compile time
+
+=item tth_converted()
+
+
+=item clean_out_math_mode()
+
+
+=item displaystyle()
+
+
+=item jsMath_converted()
+
+=item MathJax_converted()
+	- Mimics the jsMath functionality
+
+=item tex_engine()
+
+
+=item init_math_support()
+
+=item mimetex_valign()
+
+ Makes a HEAD call to /cgi-bin/mimetex.cgi via IO:: to retrieve the 
+ vertical alignment, before the subsequent call to mimetex_converted()
+ which generates the <img> tag and the corresponding image.
+
+ Input: 1.  $esc_texstring (escaped TeX to be rendered by mimetex).
+ Output: 1. $valign - number of pixels: positive or negative integer 
+            which will be included in <img> tag for mimetex image to
+            support vertical alignment of image within a line of text.
+
+ If a server is running SSL, and Apache rewrite rules are in place 
+ to rewrite requests for http to https, modification will most likely 
+ be needed for pass through for HEAD requests for /cgi-bin/mimetex.cgi. 
+
+ Example rewrite rules which rewrite all http traffic to https, 
+ except HEAD requests for /cgi-bin/mimetex.cgi are:
+
+ <IfModule mod_rewrite.c>
+     RewriteEngine On
+     RewriteLogLevel 0
+
+     RewriteCond %{HTTPS} off
+     RewriteCond %{HTTP:Host} (.*)
+     RewriteCond %{REQUEST_METHOD} !HEAD 
+     RewriteRule ^/(.*) https://%1/$1 [R=301,L]
+
+     RewriteCond %{HTTPS} off
+     RewriteCond %{HTTP:Host} (.*)
+     RewriteCond %{REQUEST_METHOD} HEAD
+     RewriteCond %{REQUEST_URI} !^/cgi-bin/mimetex.cgi
+     RewriteRule ^/(.*) https://%1/$1 [R=301,L]
+ </IfModule>
+
+=item mimetex_converted()
+
+
+=item converted()
+
+
+=item to_convert()
+
+message display
+
+=item smiley()
+
+???
+
+=item msgtexconverted()
+
+=item algebra()
+
+=item prepare_algebra()
+
+=item postprocess_algebra()
 
+=back
 
+=cut