Newbie question.
Perhaps someone familiar with this book could explain what I am not understanding...
near bottom of p. 227

else if not vectorp(action(x, ! x)) then

the trouble is, '! x', which I presume is the escape character preceding a literal,
makes no sense in the context of the code, unless, of course, I have missed something.
There's another ! in procedure whatline on p.235, that again makes no sense as the usual
character literal escape sequence.

Is there another interpretation I do not know?

Anyways, regardless if anyone could assist me, having the answer off the top of their head,
saving me a little time, I felt that with the increasing interest in Geometric Algebra and REDUCE,
and with the number of people learning these topics in self-study, it would not hurt to mention what
I feel is a fine chapter in a fine book.
Thank you,
S. Cathey

Computer Algebra with LISP and REDUCE