\begin{array} vertical alignment

[nschloe]

With

\begin{array}[t]{l}
...
\end{array}

you can vertically align a given array to top position relative to the rest of the equations; see here. Likewise c (center) and b (bottom).

Right now, equations with this syntax simply error out. It'd be nice if this was supported, or at least ignored. by KaTeX.

[edemaine]

Duplicate of #2172. I should take another look at my PR which attempted to implement this, but apparently isn't perfect.