Otared Kavian schrieb am 22.06.2021 um 15:49:
> Dear Dalyoung, dear Mikael
>
> Thank you both for your explanations: indeed this « whatever » command 
> in MetaPost is magic and very useful (I am not sure whether it is a 
> command only in MetaFun, or it exists also in the original MetaPost).

You have to go further back, whatever already existed in MetaFont.

Wolfgang