[NTG-context] Math alignment

[Hans Aberg]

The example below shows the intended output when using original TeX code (compiled with  ‘context' of TeX Live 2015): a pair of left braced formulas. The first comment shows what works in AMS-LaTeX.

However, when trying similar ConTeXt commands, I get the error shown in the comment below. What ConTeXt command might use here?

---
\setupformulas[location=left]

\starttext

\def\equlb#1{\left\{\eqalign{#1}\right.} %equation left braced

% AMS-LaTeX
%\def\equlb#1{\left\{ \begin{aligned} #1 \end{aligned}\right.} % equation left braced

% ConTeXt error: You can't use `\halign' in math mode.
%\def\equlb#1{\left\{ \startalign #1 \stopalign\right.}
%\def\equlb#1{\left\{ \startmathalignment #1 \stopmathalignment\right.}


\startformula \placeformula[JcoordDef]
 J^j:\equlb{ω^0 &→ 0 \cr ω^j &→ 0} \quad
 \equlb{ω^k &→ ω^l \cr ω^l &→ -ω^k} \stopformula

\stoptext
---