I should have posted this sooner; sorry.

I have updated the tests. This solution fails now.

Nice catch! I've updated the tests so that that posted solution fails now.

I updated the description. Thanks.

To be sure I understand the question... What to do when the below happens?

(dosteps (x 5 0 1)
  ;body
)

If that happens, do nothing; don't execute anything in the body, and don't signal an error.

If you look at line four of the 'for example' section in the description...

"A," = 0B10100000 = ‭160‬ (a + comma)

you'll notice that it is inconsistent. "(a + comma)" should be "(A + comma)". But anyway, fun kata! Thanks.