;;; 1
(defun packages-for-which-cl-is-first-on-used-list ()
  (let ((cl-pkg (find-package :cl)))
    (dolist (element (list-all-packages))
      (when (eql cl-pkg (first (package-use-list element)))
        (print (package-name element))))))

(defun packages-for-which-cl-is-on-used-list ()
  (let ((cl-pkg (find-package :cl)))
    (dolist (element (list-all-packages))
      (dolist (new-elt (package-use-list element))
        (when (eql cl-pkg new-elt)
          (print (package-name element))
          (return))))))


;;; 2


(defun find-element-and-return-list (an-item somelist)
  
  (if somelist
      (if (eql an-item (first somelist))
       somelist
        (find-element-and-return-list an-item (rest somelist)))))


;;; 3

  
(defun find-a-keyword (some-keyword some-list)
        
     (if some-list
         (do ((i 0 (+ 2 i))
              (length-of-some-list (length some-list)))
             ( (>= i length-of-some-list) nil)
           (if (eq some-keyword (nth i some-list))
               (return (nth (+ i 1) some-list))))))               


;;; 4

(defun find-first-element (object list-of-lists)
  (dolist (element list-of-lists )      
    (if (eql object (first element))
        (return element))))