add amsmath extension

[chrisjsewell]

Adds extension to specifically capture top-level amsmath latex environments

cc @choldgraf @phaustin for comment

[phaustin]

@chrisjsewell do I need to do anything special to activate the extension from myst_nb?

[chrisjsewell]

do I need to do anything special to activate the extension from myst_nb?

Few more steps until you can use it in myst-nb I'm afraid: executablebooks/MyST-NB#126 (comment)

[phaustin]

this set looks great -- is there a reason that the vertical, bracketed and parenthetical matrix environments (bmatrix, pmatrix, vmatrix) are missing? Those would be at the top of the next tier of my own list of most commonly used mathjax environments from the bottom section of https://docs.mathjax.org/en/v2.7-latest/tex.html

[chrisjsewell]

bmatrix, pmatrix, vmatrix

Ah yes, I missed these in section 4.1 of http://anorien.csc.warwick.ac.uk/mirrors/CTAN/macros/latex/required/amsmath/amsldoc.pdf. That's why I asked for your comment 😄
Added in a30e069

[phaustin]

just to flag the comment:

# eqnarray is another math environment, but is not part of amsmath, # and it is better to use align or equation+split instead 

Note that eqnarray is the default way to write systems of equations in latex. It's definitely not recommended -- i.e. http://tug.org/TUGboat/tb33-1/tb103madsen.pdf, but unfortunately it's going to be present in a lot of jupyter notebooks, and in all standard latex manuals. AMS evidently decided that simply deprecating it in mathjax wasn't worth the struggle -- I think forcing users to take their medicine isn't a bad thing, but I'd anticipate a lot of bug reports from new users, which will need to be redirected to a standard doc snippet.

[phaustin]

One other thing, I see flalign on your list, but it doesn't look like it's an environment either mathjax or katex support. That would be something that would work for the latex builder, but revert to regular align for html?

[chrisjsewell]

Note that eqnarray is the default way to write systems of equations in latex

Added in 9d22992, for users who want to be stupid 😉

[chrisjsewell]

I see flalign on your list, but it doesn't look like it's an environment either mathjax or katex support.

Yeh strange that they don't. I think it should be kept here, since the goal is to capture all top-level amsmath environments, then handle it in some way as you mention upstream in myst-parser.
There are open issue for it on both repos:

• Option to make individual aligned equations flush left like flalign KaTeX/KaTeX#1990
• Feature request: TeX environment like flalign mathjax/MathJax#1075

Note another thing to consider, which again mathjax and katex don't currently support but are good for latex PDF, would be the environments in http://mirror.ox.ac.uk/sites/ctan.org/macros/latex/contrib/breqn/breqn.pdf. Probably add this as an enhancement issue somewhere in executablebooks, for later consideration

[phaustin]

Makes sense. How much effort will it be to handle something like https://mhchem.github.io/MathJax-mhchem ?

Well we already capture $ math, so this should just be a case of loading the extension javascript in the HTML pages(?)

[choldgraf]

way to go!