Undefined control sequence \binom

[karamellpelle]

Using binomials works in preview mode, but not for the created note: "Undefined control sequence \binom". See: http://www.texpaste.com/n/s2p9dc71

PS: very nice page :)

[nvquanghuy]

Thanks for reporting the error! Will look at it real soon.

On Saturday, 23 May 2015, karamellpelle notifications@github.com wrote:

Using binomials works in preview mode, but not for the created note:
"Undefined control sequence \binom". See:
http://www.texpaste.com/n/s2p9dc71

PS: very nice page :)

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#4.

[rctay]

I did some debugging on this.

The \binom symbol requires AMSmath. Usually, this is loaded via MathJax.Hub.Config({Tex: extensions: ["AMSmath.js"], ... }) Looking at our mathjax configuration, we aren't loading it. So one should expect that \binom wouldn't work. So why does it work in the "preview" mode but not when displaying a saved note?

In the preview mode, we were loading lots of symbols for the cheatsheet on the left (via symbols.json). One of them is the \begin{align*} example under "Aligned Equations". It turns out that mathjax loads AMSmath for it - see [1]! So there you have it - why \binom works in "preview" mode but not in the saved note.

One way would be to make saved mode also show a cheatsheet, like in preview. That way, we would have all the "incidental" extensions mathjax loaded.

We could also add the AMSmath etc to extensions in the Mathjax config. It also has the benefit of making clearer what mathjax extensions we would definitely provide. However, the network trace in Chrome between preview and saved mode is still different - preview is loading more stuff, like fonts, etc. So we might still have some symbols that would be able to work in preview mode but not in saved mode.

So, we could continue tracing mathjax and dig up which extensions are being loaded, and put them in the extensions config.

I wonder if we could get mathjax to resolve the missing extension, load them, and re-render...

[1] https://github.com/mathjax/MathJax/blob/4292f9ed6bd2b57ceb740bf475d0aafbd7a8cb63/unpacked/jax/input/TeX/jax.js#L1026