Most ACL2 primitives are documented. Here is the definition of
app again, with the documented topics highlighted. All of the
links below lead into the ACL2 online documentation, 1.5 megabytes of
hyperlinked text. So follow these links around, but remember to come
(defun app (x y) (cond ((endp x) y) (t (cons (car x) (app (cdr x) y)))))
By following the link on endp we see that it is a
Common Lisp function and is defined to be the same as atom
, which recognizes non-conses. But
endp has a guard.
Since we are ignorning guards for now, we'll ignore the guard issue
So this definition reads ``to
x is an
(cdr x) and
y and then
(car x) onto that.''