New Math extension

[GiovanniSalmeri]

A new extension: https://github.com/GiovanniSalmeri/yellow-math It allows to write mathematics in AsciiMath, or in TeX. The rendering engine is the very fast KaTeX. In order to allow the use of ASCIIMath (which is not supported by KaTeX) I translated from Javascript to PHP (in order to reduce the load client-side) a program which translate ASCIIMath into TeX, and added moreover a little Javascript code which avoids the full scanning of the page by KaTeX. The result is indeed very fast (even if the AsciiMath to TeX translator could be optimised in several aspects) and the use of the extension very simple. Perhaps someone will find it useful!

[markseuffert]

Good work, I always wanted a math extension. For a long time I have been looking out for a PHP library that can render math on the server-side, something that doesn't need a client-side JavaScript library. As far as I know this is still not possible in 2021 and most math rendering is done on the client-side via KaTeX or MathJax.

Here are some suggestions/thoughts:

• Include third party JavaScript and CSS bundles, would make the extension self-hosted. The advantage with self-hosted websites is that you don't rely on third party web servers and content delivery networks, it even works when you work offline on your built-in web server.
• Use shortcut [math] and block ```math for the AsciiMath syntax, would make it more intuitive to use.
• Use shortcut [tex] and block ```tex for the TeX syntax, I know it's a violation of the usual design pattern where the shortcut/block has a name that corresponds to the extensions name, but maybe worth an exception. As an alternative you could use [mathtex] and ```mathtex for the TeX syntax.
• Can you elaborate on your thoughts for MathPlainCode, isn't inline code expected to be rendered as plain text?

Hope you find this feedback useful.

[markseuffert]

I wonder why the comparison function uses the spaceship operator, in essence it does:
return strlen($b["asciimath"]) <=> strlen($a["asciimath"]);

Perhaps the comparison function could use an arithmetic operation instead, for example:
return strlen($b["asciimath"]) - strlen($a["asciimath"]);

According to the PHP documentation, usort() does not require the exact integer values of -1, 0, +1, it expects an integer less than, equal to, or greater than zero. I am not familiar with the inner workings of PHP, but this is how most sort functions in the C/C++ standard library work. Maybe something to try out?

[GiovanniSalmeri]

I have updated the extension: PHP >= 7 is no more required. I used the spaceship operator for no particular reason, only because it is semantically clearer (at least for my eyes) than a subtraction, and because it reminds me of Star Wars 😄. Same thing for the ?? operator, now rewritten with a ternary operator. I tested with an online syntax checker and all seems to work.

Not sure how this crashed my whole site.

I am afraid this is the consequence of any syntax error (where error can also mean PHP incompatibilities) in any extension...

[zqyr]

Thanks. Another hiccup: upon installing math extension, and appending the following to a published post,

[math x=(-b+-sqrt(b^2-4ac))/(2a)]

Yellow spits out the following,

x = \frac{- b \pm \sqrt{b^{2} - 4 a c}}{2 a}

So yes, in essence your extension does seem to parse into AsciiMath Syntax. Am I missing anything within yellow-system.ini to render LaTEX expressions within post body?

[markseuffert]

Update your website, you need the latest extensions. Then AsciiMath should be converted into:

[GiovanniSalmeri]

A subtle bug has been corrected upstream by the author of the library and I backported the fix. Now there aren't any known issues open in asciimath2tex.

[markseuffert]

I changed my opinion about AsciiMath. I liked it as an input format in the beginning, but I currently don’t expect many people using it. As we discussed via email, Tex should be the input format for for inline [math] and block ```math, because that’s what most people want and that's what GitHub supports in the meantime. The needs of the many outweigh the needs of the few.

[GiovanniSalmeri]

As discussed, AsciiMath support will be soon dropped from this extension: only TeX will be supported. If and when time allows, a new(ish) extension (Asciimath or Simplemath or something similar) will support only AsciiMath for the few (like me 😊) who like it.

Since this change will be anyway breaking, just a little doubt about the coming Math: a possibility, for clarity's sake, is to rename it Tex. In this way the original suggestion of using [tex] and ```tex would be followed. Some misunderstandings possible only on the part of Italian users. Any opinion?

[GiovanniSalmeri]

The Math extension has been (finally...) updated. AsciiMath support has been dropped and the new extension Mu supports only AsciiMath. As this is a breaking change, here is a quick reminder for those who are using the old Math extension:

• If you use AsciiMath, install Mu and rename in your pages [math and ``` math to [mu and ``` mu
• If you use TeX/LaTeX, after installing the new version of Math rename in your pages [mathtex and ``` mathtex to [math and ``` math

Any comments appreciated!

[markseuffert]

I think this is perplexing because a "double root" is not a compound word in the English language. In Sweden there is a different mathematical tradition. The quadratic equation is described as always having two solutions in the real or complex numbers. Two identical real numbers, two different real numbers, two complex numbers. Keep the easter egg. 😄

[markseuffert]

Thank you very much for mentioning the Italian terminology. I was curious what you meant. This weekend I read the Italian Wikipedia on mathematics, translated into English, a pleasure to read. What struck me often as positive was the historical context and the clear language. Such a joy to read. For example see quadratic equation and M.C. Escher.

[GiovanniSalmeri]

As foretold, I have updated the experimental extension Mu. Now it has a very simple mechanism for numbering and cross-referencing expressions. I added it because numbering and cross-referencing mathematical expressions is the rule, not the exception (even though there are among experts different opinions about which expressions should be numbered 1 2 3).

About Math, I see now three different options.

A. Relying on LaTeX's own numbering mechanism, which works out of the box in KaTeX. Well, almost out of the box: cross-referencing is presently supported only with a third-party script, which should be merged with math.js and tested. I see three drawbacks: 1. the LaTeX syntax is cumbersome (one should write [math \begin{equation}\label{quad}ax^2+bx+c=0\end{equation}] only for numbering an espression, and [math \eqref{quad}] for referencing it; 2. the above script adds a new constraint ("For numbering to work correctly ... each line in a numbered environment either needs to contain a \label or a \nonumber"). 3. references will be composed in math font, which typographically makes little sense.

B. Adding the same mechanism now implemented in Mu. One could simply write [math ax^2+bx+c=0 #quad] for numbering an expression and [#quad] for referencing it. I have tried this in a modified Math and it works well.

C. Neither A nor B, leaving all as it is. It is already possible to number expressions with LaTeX syntax, cross-referencing can be done by hand (but adding a link between reference and expression would be very awkward). And those who wish a handier method will switch to Mu 😁

Any opinions on which one is best?

What struck me often as positive was the historical context and the clear language. Such a joy to read.

OT: My father would have been very glad to hear this! Mathematics was his passion and in his youth he published many papers in Italian mathematical journals (now none exists anymore). He was very proud when he discovered that Donald Knuth had cited a work of his (in Italian!) in an article about mathematical notation. When he passed away I discovered a copybook with a handwritten little treatise on "quasi-algebraic curves" (an invention of his), which later he only partially published. Even if he wasn't particularly interested in informatics, my passion is surely due to the mathematics which I saw around me.

[markseuffert]

My advice for shortcuts would be to do as little as possible.

The following Markdown syntax might work for your extension. You can have inline shortcuts without support for cross-references and numbering, perhaps see [math \Delta = b^2 - 4ac] as a special form of text formatting for mathematical symbols. You can have code block shortcuts with support for cross-references and numbering, code blocks allow special attributes, which could be used to activate numbering. About arguments without quotes being confusing for new users. It's the first thing new users will encounter, for example [edit - You can edit this page]. The additional hyphen bothers me, it was introduced for readability as far as I know and I have been thinking about removing it for a long time. I understand the desire for symmetry/beauty/consistency. Fortunately we are talking about mathematics and not about particle physics, perhaps see inline shortcuts with one argument as a special form. One that is useful. At the end of the day choose the Markdown syntax that fits best into your workflow.

Hope this helps.

[GiovanniSalmeri]

see inline shortcuts with one argument as a special form

You found a good argument to convince me: I dislike exceptions, but special forms are fine 😁. I have accordingly updated the extension: syntax simplified, cross-referencing added, custom escape dropped (now closing brackets are ] or \rbrack), a bit of CSS added, many more examples in the Readme. Now all seems in good shape 😊