Dear Hans,

Thanks for the patch.  It runs without errors again.  However, another problem surfaced.  In the MWE
below the second column of the matrix is no longer centred as it should be.

current version: 2017.09.08 17:24

Cheers, Henri

---

\starttext

\placeformula
\startformula
   \startmathmatrix
     \NC long line \NC 1 \NR
     \NC 1 \NC long line \NR
   \stopmathmatrix
\stopformula

\stoptext

On Mon, 2017-09-11 at 10:03 +0200, Hans Hagen wrote:
> On 9/11/2017 6:59 AM, Henri wrote:
> > 
> > Dear devs,
> > 
> > Thank you very much for fixing this one
> > https://mailman.ntg.nl/pipermail/ntg-context/2017/089790.html
> > Unfortunately it seems like you broke substack and mathmatrix on the way.  MWE below fails
> > with version 2017.09.08 17:24
> > 
> > Cheers, Henri
> > 
> > ---
> > 
> > \starttext
> > 
> > \placeformula
> > \startformula
> >    \sum_{\startsubstack
> >      \NC k \NR
> >      \NC \omega_n \NR
> >    \stopsubstack}
> > \stopformula
> > 
> > \placeformula
> > \startformula
> >    \startmathmatrix[left=\left|,right=\right|]
> >      \NC 0 \NC 1 \NR
> >      \NC 1 \NC 0 \NR
> >    \stopmathmatrix
> >    = -1 .
> > \stopformula
> > 
> > \stoptext
> % no tagging yet : how is it supposed to be coded? no time now anyway
> 
> \unexpanded\def\startsubstack
>    {\begingroup
>     \vcenter\bgroup
>     \baselineskip\mathstacktotal
>     \lineskip\mathstackvgap
>     \lineskiplimit\lineskip
>     \mathsurround\zeropoint
>     \everycr\emptytoks
>     \let\NC\relax
>     \let\MC\relax
>     \let\NR\crcr
>  
> \halign\bgroup\hfil\normalstartimath\scriptstyle\alignmark\alignmark\normalstopimath\hfil\crcr}
> 
> \def\stopsubstack
>    {\crcr
>     \egroup
>     \egroup
>     \endgroup}
> 
> 
> -----------------------------------------------------------------
>                                            Hans Hagen | PRAGMA ADE
>                Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
>         tel: 038 477 53 69 | www.pragma-ade.nl | www.pragma-pod.nl
> -----------------------------------------------------------------