# [NTG-context] Math in metapost

Hans Hagen pragma at wxs.nl
Wed Nov 30 23:01:00 CET 2011

On 30-11-2011 20:59, Hans van der Meer wrote:
> I would like to put some math in metapost pictures. For the moment I am using textext for the typesetting in my metapost macro: pic := textext("\setbox0=\hbox{\color["&textcolor&"]"&labeltext&"}\dp0=0pt\box0");
> picture pic will be placed in the metapost figure.
>
> Simple math like $p=2$ works fine, but the system chokes on something like the following matrix:
> $\pmatrix{p_{0|0}\cr}$ (it does fine in ConTeXt itself).
>
> The error is: ! Only one # is allowed per tab.
> system>  tex>  error on line 6 in file Info/kanaalmatrix.tex: Only one # is allowed per tab ...
>
> Perhaps I am too optimistic about textext's possibilities. But how can I accomplish the placement of these and more elaborate formulae in metapost pictures using ConTeXt? It is of the essence for a series of Powerpoint slides I am preparing, wheein these formulae must be placed as individual pictures.

you can patch pmatrix:

\unexpanded\def\pmatrix#1%
{\left(\matrix{#1}\right)}

(i'll make the lot unexpandable)

btw, for large chunks you can consider using setups

\startsetups lots-of-math

\stopsetups

... \textext("\setup[lots-of-math]")

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