;; test-fn: #'(lambda(x) (and (integerp x) (> x 0)))
;; sort-fn #'(lambda (x y) (< x y))`

(defmacro combine (l1 l2)
  `(nconc ,l1 ,l2))

(defun listproc (l test-fn sort-fn)
  (cond ((null l) nil)
	((atom l) (if (funcall test-fn l) (list l) nil))
	(t (sort (combine (listproc (car l) test-fn sort-fn)
			  (listproc (cdr l) test-fn sort-fn))
		 sort-fn))))

(defun posint (l)
  (listproc l 
	    #'(lambda(x) (and (integerp x) (> x 0)))
	    #'(lambda(x y) nil)))