I was looking for a procedure that returns the length of the spine of a dotted
list, and saw that length+ will do this. But according to the SRFI it’s not a
valid argument. And a brief search through the archives reveals a message from
Olin stating that it should signal an error if given such an argument, as most
list procedures do.

There are several ways to resolve this, including doing nothing. I don’t have
a strong opinion on the right action, though obviously in my current situation
I’d like it to work on dotted lists. :)