# [NTG-context] Calculating a value in metapost, and using it in ConTeXt

Hans Hagen pragma at wxs.nl
Wed May 27 01:18:50 CEST 2015

```On 5/26/2015 9:17 PM, Kate F wrote:
> Hello,
>
> Is it possible to calculate the position of something in Metapost, and
> to export that value to TeX such that I can use it in setups and
> things?

it depends on what you want to calculate

\startMPcalculation
path p, q;

h := PaperHeight;
w := PaperWidth;

p = (0, 0) -- (w, .5h);
q = (0, h) -- (w, 0);

z0 = p intersectionpoint q;

passvariable("z",ypart z0) ;
\stopMPcalculation

\setuplayout
[topspace=0pt,
height=\MPrunvar{z}bp]

\showgrid

\starttext
xyz:\MPrunvar{z}
\stoptext

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