On 13/10/2020 19:09, LARONDE Thierry wrote:
> Can you simply point me to the (u)pTeX .ch file and point me to the
> initial documentations/articles that list the primitives
> needed and what they have to achieve?


contains I think all of the utility primitives. Quite a bit of code is 
devoted to setting up random numbers: it's basically a self-contained 
block. The other parts are actually more interesting from the point of 
view of integrating to other things.