% Expectation symbol
\DeclareMathOperator*{\E}{\mathbb{E}}

to your LaTeX preamble and you’re done. You’ll also need to add \usepackage{amsmath} or in LyX to tick “Use AMS math package” under Document->Settings->Math Options.

Using the starred version of \DeclareMathOperator makes sure subscripts goes beneath the symbol in display mode.

A tiddler with LaTeX equations.

I quickly realized MathJax will be a perfect fit for TiddlyWiki which is also based on pure Javascript. It will allow me to enter complex formulas in tiddlers and still be able to carry my wiki anywhere with me, independent of a real TeX installation. I searched the web for an existing MathJaX plugin for TiddlyWiki but I came up empty handed (I did find some links, but they referenced pages that no longer exist). So I regarded it as a nice opportunity to begin writing some plugins for TiddlyWiki and created the MathJaxPlugin which integrates MathJax with TiddlyWiki.

As I don’t have an online TiddlyWiki, you’ll won’t be able to import the plugin, instead you’ll have to install it manually (which is pretty simple).

Start by creating a new tiddler named MathJaxPlugin, and tag with systemConfig (this tag will tell TiddlyWiki to execute the JS code in the tiddler, thus making it a plugin. Now copy the following code to the tiddler content:

/***
|''Name:''|MathJaxPlugin|
|''Description:''|Enable LaTeX formulas for TiddlyWiki|
|''Version:''|1.0.0|
|''Date:''|Jun 25, 2011|
|''Source:''|http://www.guyrutenberg.com/2011/06/25/latex-for-tiddlywiki-a-mathjax-plugin|
|''Author:''|Guy Rutenberg|
|''License:''|[[BSD open source license]]|
|''~CoreVersion:''|2.5.0|
 
Currently the plugin supports the following delemiters:
* """$$""".."""$$""" - Inline equations
* """\(""".."""\)""" - Inline equations
* """\[""".."""\]""" - Display equations
***/
 
//{{{
config.extensions.MathJax = {
  mathJaxScript : "http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML",
  // uncomment the following line if you want to access MathJax using SSL
  // mathJaxScript : "https://d3eoax9i5htok0.cloudfront.net/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML",
  displayTiddler_old : story.displayTiddler,
  displayTiddler: function(TiddlerName) {
    config.extensions.MathJax.displayTiddler_old.apply(this, arguments);
    MathJax.Hub.Queue(["Typeset", MathJax.Hub]);
  }
};
 
jQuery.getScript(config.extensions.MathJax.mathJaxScript, function(){
    MathJax.Hub.Config({
      extensions: ["tex2jax.js"],
      "HTML-CSS": { scale: 100 }
    });
 
    MathJax.Hub.Startup.onload();
    story.displayTiddler = config.extensions.MathJax.displayTiddler;
});
 
config.formatters.push({
	name: "mathJaxFormula",
	match: "\\\\\\[|\\$\\$|\\\\\\(",
	//lookaheadRegExp: /(?:\\\[|\$\$)((?:.|\n)*?)(?:\\\]|$$)/mg,
	handler: function(w)
	{
		switch(w.matchText) {
		case "\\[": // displayed equations
			this.lookaheadRegExp = /\\\[((?:.|\n)*?)(\\\])/mg;
			break;
		case "$$": // inline equations
			this.lookaheadRegExp = /\$\$((?:.|\n)*?)(\$\$)/mg;
			break;
		case "\\(": // inline equations
			this.lookaheadRegExp = /\\\(((?:.|\n)*?)(\\\))/mg;
			break;
		default:
			break;
		}
		this.lookaheadRegExp.lastIndex = w.matchStart;
		var lookaheadMatch = this.lookaheadRegExp.exec(w.source);
		if(lookaheadMatch && lookaheadMatch.index == w.matchStart) {
			createTiddlyElement(w.output,"span",null,null,lookaheadMatch[0]);
			w.nextMatch = this.lookaheadRegExp.lastIndex;
		}
	}
});
//}}}

After saving the tiddler, reload the wiki and the MathJaxPlugin should be active. You can test it by creating a new tiddler with some equations in it:

This is an inline equation $$P(E)   = {n \choose k} p^k (1-p)^{ n-k}$$ and this is a displayed equation:
\[J_\alpha(x) = \sum_{m=0}^\infty \frac{(-1)^m}{m! \, \Gamma(m + \alpha + 1)}{\left({\frac{x}{2}}\right)}^{2 m + \alpha}\]

Which should result in the tiddler that appears in the above image.

Update 20110819: Removed debugging code from the plugin.

 \lyxframeend
                 {}\lyxframe{Outline}
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

After comparing my document to example (working) beamer documents I’ve found out that you must have an EndFrame command after your last frame.Too bad it wasn’t documented anywhere I’ve found as this little thing drove me crazy.

At first, I’ve tried to use the English dash and en-dash but result weren’t satisfactory. Both of them were too light and positioned too low to be used in an Hebrew text written in the Culmus fonts (see screenshot).

So finally, I’ve decided to write a simple macro to emulate a Kav-Mafrid for the David font.

\newcommand{\dd}{\lower0.17em\hbox{-\kern-0.13em-}}

The command works by kerning two Hebrew, Maqaf’s, together (with a slight overlap to adjust width), and lowering their position to the middle of the line.

In the following screensot the first line features the Frank Ruehl font and it\’s Maqaf and Kav-Mafrid. The second line featured the david font with a Maqaf and the missing Kav-Mafrid ligature. The third line features the David font with English dash and en-dash. The last line uses David with the regular Maqaf and the \dd{} macro.

Different dash examples

As it can be seen, the \dd{} macro does provide a good alternative for the Kav-Mafrid. However this solution isn’t perfect. One can improve the macro by detecting if the Kav-Mafrid ligature is present in the current font and if so, use it instead of the kerned one. This would enable one to use the macro and safely switch fonts, knowing he will always get the best Kav-Mafrid possible.

The problem is that because TeX doesn’t store information regarding the direction of text inside the dvi, RTL text is actually stored in reverse. When a link is inserted in such text, the command to start the link ends up after the command to end the link, which is problematic. When trying to compile such document with pdfTex it throws errors like:

! pdfTeX error (ext4): pdf_link_stack empty, \pdfendlink used without \pdfstart

On the otherhand XeTeX behaves a little nicer and compiles the document, but the wrong parts of the text are marked as links.

My workaround basically changes the order of the start and end link commands. Thus, in RTL text the commands get reversed and actually end up in the correct order. The workaround doesn’t support links spanning multiple lines and color links (although link border is supported). Further work needs to be done in order to support links in the table of contents. I could get it to work only in LTR mode (which isn’t good). You should insert the following code to your preamble in order to enable the workaround.

\makeatletter
\def\hyper@link#1#2#3{%
  \if@rl
    \setLR
      \begingroup
      \hyper@linkend
        #3
      \hyper@linkstart{#1}{#2}
    \setRL
  \else
    \hyper@linkstart{#1}{#2}
        #3
    \hyper@linkend
  \fi
}
\makeatother

I’ll also note that in order to generate correct pdf bookmarks (not in gibberish), you should set unicode=false in the hyperref‘s options.

You can find a working example bellow (and the corresponding PDF output here).

\documentclass{article}
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{bidi}
 
\usepackage[unicode=false,
 bookmarks=true,bookmarksnumbered=false,bookmarksopen=false,
 breaklinks=false,pdfborder={0 0 1},backref=false,colorlinks=false]
 {hyperref}
 
\makeatletter
\def\hyper@link#1#2#3{%
  \if@rl
    \setLR
      \begingroup
      \hyper@linkend
        #3
      \hyper@linkstart{#1}{#2}
    \setRL
  \else
    \hyper@linkstart{#1}{#2}
        #3
    \hyper@linkend
  \fi
}
\makeatother
\setromanfont{Times New Roman}
 
\begin{document}
\setRL
\title{בדיקה}
\author{גיא רוטנברג}
\date{}
\maketitle
\pagebreak{}
 
\section{סעיף ראשון}\label{testlabel}
\subsection{תת-סעיף ראשון}\label{testlabel2}
 
לה לה
 
לי לי
 
לו לו
 
\pagebreak{}
\section{סעיף שני}
\subsection{תת-סעיף ראשון}
 
לה לה
 
\subsection{תת-סעיף שני}
 
לי לי
חלק \ref{testlabel}
אבגד
\hyperref[testlabel2]{בדיקה ארוכה}
 
\setLR
This is a test for LTR links. See section \ref{testlabel} and \hyperref[testlabel2]{long label}.
\end{document}

For sometime before letting go of the issue, I’ve tried to correct the direction of the label. It could have been fixed by marking the float as English text in LyX (I use it for editing Hebrew papers, as it makes editing multi-lingual texts easy), effectively adding \selectlanguage{english} before the \begin{algorithm} line. However, it resulted in display mess in LyX and some LaTeX errors when compiling (also it seemed LaTeX could complete the first pass).

Today, I’ve decided to tackle and solve the problem for a new paper I’m writing. After searching a bit for a way to override the Algorithm environment label, I’ve found a general way to override a float label in LaTeX:

\floatname{floatname}{floatlabel}

So for our case it would look like this:

\floatname{algorithm}{אלגוריתם}

You should put it in your LaTeX preamble (Documents->Settings in LyX). This neatly fixes the problem (see screenshot below).

While LyX doesn’t support many of the great packages out there like mathtools (which I really hope it will someday), you can add some support to your documents. At the beginning of the document insert a comment, via Insert->Note->Comment. Inside the newly created comment insert a math-macro via Insert->Math->Macro. In the name part, put the name of the command you want to add support for. In the second box (caption LyX), use existing LyX commands to mimic how the macro will look like. For example, this is what it looks like for the \coloneqq macro (from the great mathtools package):

After adding the math macro in the comment, when you will use the macro inside formulas it will display nicely:

A little explanation how things work. When you define a math macro in LyX, LyX does two things:

1. Inserts LaTeX code to create the macro.
2. Displays the macro nicely when editing the document.

While the latter is desirable, the former is problematic. If LyX inserts LaTeX code to define the existing macro, it will cause errors. So when you put the LyX macro in the comment environment, the code LyX generates gets ignored and only the second, desirable, outcome is achieved.

To my surprise, Graphviz (and especially the dot utility) turned out to be the (almost) perfect tool for the job. It lets you describe the graph in a simple text-based way, and it handles the graph layout by himself. This is somewhat like LaTeX but for graphs (you concentrate on content not layout).

My Finite Automata needed no manual tweaking and resulted in a very nice graphs. For more complicated State Machines it’s sometimes necessary to do some manual tuning. The commands I found most useful to tweak the graph were:

• Grouping nodes to be in the same level – { rank="same"; "q1"; "q2"; "q3"}. The other options for rank can affect how the group is positioned relative to the other nodes in the graph (source, above all, sink bellow all).
• Adding weight to edges – q1 -> q2 [weight="10"]. This affects the cost of strecting the edge. The higher the weight the straighter the edges will be.
• Adding invisible edges – q1 -> q3 [style="invis"]. This allowed me to control the order of the nodes in the same rank (height).

Last but not least Graphivz can generate the graphs in variety for formats including eps, pdf and svg (which allows post-processing with inkscape).

LaTeX Error: Command \textquotedbl unavailable in encoding HE8

This could be solved by adding the following line to your LaTeX preamble:

\let\textquotedbl="

This line will define the \textquotedb to be the double quotation mark, and the document will compile look the same as it looked in older versions of LyX.

The general macro is the \relat. It takes two arguments, the relation and an expression where the relation takes place (the “at”). The equality-at macro, \eqat is a specific case of \relat. I’ve created it because it is commonly used and only requires passing the “at” argument.

Here is the LaTeX code for the macros.

\newcommand{\relat}[2]{\mathrel{\bigg|_{\mathrlap{#2}}\mathrlap{#1}\hphantom{{}_{#2}}}}
\newcommand{\eqat}[1]{\mathrel{\bigg|_{\mathrlap{#1}}\mathrlap{=}\hphantom{{}_{#1}}}}

This is a basic example of how to use the macros. It should also give you an idea how they look.

documentclass{article}
\pagestyle{empty}
\usepackage{mathtools}
 
\newcommand{\relat}[2]{\mathrel{\bigg|_{\mathrlap{#2}}\mathrlap{#1}\hphantom{{}_{#2}}}}
\newcommand{\eqat}[1]{\mathrel{\bigg|_{\mathrlap{#1}}\mathrlap{=}\hphantom{{}_{#1}}}}
 
\begin{document}
 
\[
\Delta=\left[\begin{array}{cc} P & Q\\ f' & g'\end{array}\right]
\eqat{\Gamma}
\left[\begin{array}{cc} -2t & 4t\\ 1 & -2\end{array}\right]
\]
\[
\cos x \relat{\leq}{x=\frac{\pi}{3}} \frac{\sqrt{@}}{2}
\]
 
\end{document}

And the output for the example is