On Thu, 18 Mar 2021, Weber, Matthias wrote:
> Hello,
>
> Is it possible to nest cases in math, like so:
In principle, it should be. But we never tested this and I suspect that there
is some macro which doesn't get initialized correctly in nested cases.
> \starttext
> \startformula
> x=
> \startcases[align={right,left},distance=3pt]
> \NC a \NC =
> \startcases[align={right,left},distance=3pt]
> \NC 1 \NC \text{case a1} \NR
> \NC 2 \NC \text{case a2} \NR
> \stopcases
> \NR
> \NC b \NC =
> \startcases[align={right,left},distance=3pt]
> \NC 3 \NC \text{case b3}\NR
> \NC 4 \NC \text{case b4}\NR
> \stopcases
> \NR
> \stopcases
> \stopformula
> \stoptext
>
> I get an error about a missing $ when I try a nested start/stop-cases.
The missing $ error is because the cases environment uses two column separators
(for the second column): \NC for "normal text column" and \MC for "math
column". This is so that in the typical case, you can just use:
\startformula
x = \startcases
\NC 1 \NC case $a_1$ \NR
\NC 2 \NC case $a_2$ \NR
\stopcases
\stopformula
So, in your cases, you should have used:
\starttext
\startformula
x=
\startcases[align={right,left},distance=3pt]
\NC a \MC =
\startcases[align={right,left},distance=3pt]
\NC 1 \NC case a1 \NR
\NC 2 \NC case a2 \NR
\stopcases
\NR
\NC b \MC =
\startcases[align={right,left},distance=3pt]
\NC 3 \NC case b3\NR
\NC 4 \NC case b4\NR
\stopcases
\NR
\stopcases
\stopformula
\stoptext
But, something goes wrong and that doesn't work either (with a different error
message). I suspect that something is not getting initialized correctly at
\startcases and will look into that.
Aditya
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