Adding Python/Clojure-style list comprehensions to Common Lisp

gistfile1.lisp

;; Beginner's attempt at adding list comprehensions to Common Lisp.

;; Examples:
;; (for ((x '(1 2 3))) (* x x)) # => (1 4 9)
;; (for ((x '(1 2)) (y '(a b))) (list x y)) # => ((1 a) (1 b) (2 a) (2 b))

(defun foldr (f z xs)
  (cond ((null xs) z)
        (t (funcall f (car xs) (foldr f z (cdr xs))))))

;; Works by nesting calls to dolist. The dolists push each evaluation of
;; the macro's body parameter onto an accumulator, which is then
;; reversed in the ultimate expansion.
(defmacro for (bindings body)
  (let ((acc (gensym)))
    (cond ((null bindings) (error "needs at least one binding!"))
          (t (let ((expansion
                    (foldr (lambda (b expr)
                             `(dolist ,b ,expr))
                           `(push ,body ,acc)
                           bindings)))
               `(let ((,acc nil))
                  ,expansion
                  (nreverse ,acc)))))))

I know it's an exercise in learning, but loop already does way more than anyone could possibly even want to do.