Is there a RPN operation that does nothing? (NOP)

[PeterP]

(01-04-2018 06:19 AM)hth Wrote:  The Text-0 instruction in the HP-41 pops in my mind as something that was suggested in the PPC days. It has to be created by synthetic means.

Håkan

IIRC, for the HP41 this Text-0 is the fastest, shortest 'NOP', followed by the Lbl0-Lbl14, which is also one byte but slightly more wasteful as long programs often need more than 15 Lbl, meaning if one is used for a NOP, one needs to revert to 2-byte LBLs.
Non-Synthetic and not Lbl-wasteful is Sto St X (or X<> ST X).
Our kind host Dave has put up a fantastic "Synthetic 101" here which shows how to get a byte grabber all the way to 'LB'.