When ISZ/DSZ > ISG/DSE

[Gene]

Ran across something interesting (to me at least) in an HP KeyNotes issue.

The situation was on the HP-67, the I register contained either a zero or one. Goal was to use ISZ/DSZ to switch it. Think of it as a brain-teaser:

"The X register contains either a zero or one. Flip the value without using any digit keys or X=? test conditionals."

The solution presented was...

ISZ
DSZ
DSZ
ISZ

which works. Then I started thinking. That's hard to do on the HP41 style structure.

ISG won't work here. Thoughts?

Try it on your HP67 or an emulator and help me think through how to do it this way on an HP41. No X=Y? or X=0? conditionals allowed. :-)