Hello Abderrahim El Khou,
if it possible i want a tutorial how to write my own thorn if it is thank you a lot
Kranc has an example (the SimpleWave.m one) in:
http://kranccode.org/documentation.html
though note that it uses the `Bin/kranc` wrapper so that all required Mathematica packages are being found.
There are a number of recorded tutorials on how to write a new thorn that you can find in:
https://www.youtube.com/playlist?list=PLRxi-yB7cTGc6_RtPA8g3qm2XOGfmvkoH
for example:
https://youtu.be/PcuPhODh34o?si=tAaM54bRT584N7Qo
There's also the CreatingANewThorn-*.ipyb notebooks in:
https://github.com/EinsteinToolkit/jupyter-et/tree/master/tutorial-server/no...
which are actually used in the recording above.
Yours, Roland