function iota in common lisp

iota.lisp

(defun iota (m &optional (n 1) (step 1))
	(defun iter (m n lst)
		(cond ((> n m) (reverse lst))
			(t (iter m (+ n step) (cons n lst)))))
	(iter m n nil))

No. Don't use defun inside another defun. The inner defun will create or overwrite a global function, so as soon as you use the same "inner" function name elsewhere, the two will constantly trip over each other!

Use labels here (flet in other cases).

Also, don't assume tail call elimination for portable Common Lisp code. This will blow the stack on ABCL, for example, because ABCL cannot provide TCO due to the JVM's design.

Finally, always define standard ranges as inclusive-exclusive. See Dijkstra.

A better definition of iota is: (defun iota (end &optional (start 0) (step 1)) (loop :for n :from start :below end :by step :collect n)).

Finally, use the library of Alexandria (available from Quicklisp), which gives you a iota that also handles numeric contagion consistenty.