I’m pretty sure it’s because the lisp that book makes isn’t an exact lisp; There are many features lacking and some fundamental concepts are wrongly implemented; However for developing C skills, it’s pretty good. Wouldn’t recommend learning Lisp with that though.
The 900-something lines of C code documented by the book Interpreting Lisp, which can now be found on Github, is not something I would recommend for teaching C beginners.
From a best practices point of view, it is pretty awful.
