Generator/Exponential: Difference between revisions

=={{header|Common Lisp}}==

<lang lisp>(defun take (seq &optional (n 1))

(values-list (loop repeat n collect (funcall seq))))

(defun power-seq (n)

(let ((x 0))

(lambda () (prog1 (expt (incf x) n)))))

(defun filter-seq (s1 s2) ;; remove s2 from s1

(let ((x1 (take s1)) (x2 (take s2)))

(lambda ()

(tagbody g

(if (= x1 x2)

(progn (setf x1 (take s1) x2 (take s2)) (go g)))

(if (> x1 x2)

(progn (setf x2 (take s2)) (go g))))

(prog1 x1 (setf x1 (take s1))))))

(let ((2not3 (filter-seq (power-seq 2) (power-seq 3))))

(take 2not3 20) ;; drop 20

(princ (multiple-value-list (take 2not3 10))))</lang>