Blog de Frédéric

Tag - bison

Tuesday, February 25 2014

TeXZilla 0.9.4 Released

update 2014/03/11: TeXZilla is now available as an npm module.

Introduction

For the past two months, the Mozilla MathML team has been working on TeXZilla, yet another LaTeX-to-MathML converter. The idea was to rely on itex2MML (which dates back from the beginning of the Mozilla MathML project) to create a LaTeX parser such that:

• It is compatible with the itex2MML syntax and is similarly generated from a LALR(1) grammar (the goal is only to support a restricted set of core LaTeX commands for mathematics, for a more complete converter of LaTeX documents see LaTeXML).
• It is available as a standalone Javascript module usable in all the Mozilla Web applications and add-ons (of course, it will work in non-Mozilla products too).
• It accepts any Unicode characters and supports right-to-left mathematical notation (these are important for the world-wide aspect of the Mozilla community).

The parser is generated with the help of Jison and relies on a grammar based on the one of itex2MML and on the unicode.xml file of the XML Entity Definitions for Characters specification. As suggested by the version number, this is still in development. However, we have made enough progress to present interesting features here and get more users and developers involved.

Quick Examples

\frac{x^2}{a^2} + \frac{y^2}{b^2} = 1

$\frac\left\{x^2\right\}\left\{a^2\right\} + \frac\left\{y^2\right\}\left\{b^2\right\} = 1$

∑_{n=1}^{+∞} \frac{1}{n^2} = \frac{π^2}{6}

$\sum _\left\{n=1\right\}^\left\{+\infty \right\} \frac\left\{1\right\}\left\{n^2\right\} = \frac\left\{\pi ^2\right\}\left\{6\right\}$

س = \frac{-ب\pm\sqrt{ب^٢-٤اج}}{٢ا}

$س = \frac\left\{-ب\pm\sqrt\left\{ب^٢-٤اج\right\}\right\}\left\{٢ا\right\}$

Live Demo / FirefoxOS Web app

A live demo is available to let you test the LaTeX-to-MathML converter with various options and examples. For people willing to use the converter on their mobiles a FirefoxOS Web app is also available.

Using TeXZilla in a CommonJS program or Web page

TeXZilla is made of a single TeXZilla.js file with a public API to convert LaTeX to MathML or extract the TeX source from a MathML element. The converter accepts some options like inline/display mode or RTL/LTR direction of mathematics.

You can load it the standard way in any Javascript program and obtain a TeXZilla object that exposes the public API. For example in a commonJS program, to convert a TeX source into a MathML source:

  var TeXZilla = require("./TeXZilla");
console.log(TeXZilla.toMathMLString("\\sqrt{\\frac{x}{2}+y}"));


or in a Web Page, to convert a TeX source into a MathML DOM element:

  <script type="text/javascript" src="TeXZilla.js"></script>
...
var MathMLElement = TeXZilla.toMathML("\\sqrt{\\frac{x}{2}+y}");


One of the goal of TeXZilla is to be integrated in Mozilla add-ons, allowing people to write cool math applications (in particular, we would like to have an add-on for Thunderbird). A simple Firefox add-on has been written and passed the AMO review, which means that you can safely include the TeXZilla.js script in your own add-ons.

TeXZilla can be used as an addon-sdk module. However, if you intend to use features requiring a DOMParser instance (for example toMathML), you need to initialize the DOM explicitly:

  var {Cc, Ci} = require("chrome");
TeXZilla.setDOMParser(Cc["@mozilla.org/xmlextras/domparser;1"].
createInstance(Ci.nsIDOMParser));


  TeXZilla.setDOMParser(Components.
classes["@mozilla.org/xmlextras/domparser;1"].
createInstance(Components.interfaces.nsIDOMParser));


Using TeXZilla from the command line

TeXZilla has a basic command line interface. However, since CommonJS is still being standardized, this may work inconsistently between commonjs interpreters. We have tested it on slimerjs (which uses Gecko), phantomjs and nodejs. For example you can do

  $slimerjs TeXZilla.js parser "a^2+b^2=c^2" true <math xmlns="http://www.w3.org/1998/Math/MathML" display="block"><semantics><...  or launch a Web service (see next section). We plan to implement a stream filter too so that it can behave the same as itex2MML: looking the LaTeX fragments from a text document and converting them into MathML. Using TeXZilla as a Web Server TeXZilla can be used as a Web Server that receives POST and GET HTTP requests with the LaTeX input and sends JSON replies with the MathML output. The typical use case is for people willing to perform some server-side LaTeX-to-MathML conversion. For instance, to start the TeXZilla Webserver on port 7777: $ nodejs TeXZilla.js webserver 7777
Web server started on http://localhost:7777


Then you can sent a POST request:

  $curl -H "Content-Type: application/json" -X POST -d '{"tex":"x+y","display":"true"}' http://localhost:7777 {"tex":"x+y","mathml":"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"...  or a GET request: $ curl "http://localhost:7777/?tex=x+y&rtl=true"
{"tex":"x+y","mathml":"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"...


Note that client-side conversion is trivial using the public API, but see the next section.

Web Components Custom Element <x-tex>

We used the X-Tag library to implement a simple Web Components Custom Element <x-tex>. The idea is to have a container for LaTeX expressions like

  <x-tex dir="rtl">س = \frac{-ب\pm\sqrt{ب^٢-٤اج}}{٢ا}</x-tex>

that will be converted into MathML by TeXZilla and displayed in your browser: $س = \frac\left\{-ب\pm\sqrt\left\{ب^٢-٤اج\right\}\right\}\left\{٢ا\right\}$. You can set the display/dir attributes on that <x-tex> element and they will be applied to the [itex] element. Instances of <x-tex> elements also have a source property that you can use to retrieve or set the LaTeX source. Of course, the MathML output will automatically be updated when dynamic changes occur. You can try this online demo.

CKEditor Plugins / Integration in MDN

Finally, we created a first version of a TeXZilla CKEditor plugin. An online demo is available here. We already sent a pull request to Kuma and we hope it will soon enable users to put mathematical mathematical formulas in MDN articles without having to paste the MathML into the source code view. It could be enhanced later with a more advanced UI.

Thursday, September 16 2010

An XPCOM component to parse mathematical expressions into MathML (part 1)

I have started to write a math parser usable by Mozilla-based applications. In particular, this could help to add math editing features to Mozilla's editors (BlueGriffon™, Komposer or Thunderbird etc). Of course, it will also be usable by Mozilla's extensions, such that Firemath. I will probably give more details in subsequent blog posts but the main ideas are given in that one.

First, the parser is usable through classical XPCOM calls. With the current interface, we get something like (in Javascript):

mathparser =
Components.classes['@mozilla.org/editor/mathparser;1'].
createInstance(Components.interfaces.nsIMathParser);

node = mathparser.parse(document, input,
Components.interfaces.nsIMathParser.MATHPARSER_MODE_SIMPLE);

where input is a string representing a mathematical formula and node is the output MathML tree. Note the third parameter of the parse function, which allows to choose a parser mode. For the moment, I have only written one for very basic formulas. However, I plan to add at least a LaTeX-like mode.

As an example, if we provide the following input strings "{∑_{i=1}^{+∞} 1/n^2} = π^2/6" and "{∫_0^{+∞} {ⅆx}/{4(x+1)√x}} = π/4" the parser outputs:

$\sum _{i=1}^{+\infty }\frac{1}{{n}^{2}}=\frac{{\pi }^{2}}{6}$${\int }_{0}^{+\infty }\frac{dx}{4\left(x+1\right)\sqrt{x}}=\frac{\pi }{4}$

Note that the core engine is produced using the famous parser generator Bison and hence it will be easy to adapt the work of itex2MML. The lexical analyzer is written directly and we get a very nice feature: unicode support! If people are interested, I have some patches applyable to mozilla-central...