tasks a-s

Task/Power-set/Common-Lisp/power-set-1.lisp

@@ -0,0 +1,8 @@
+(defun power-set (s)
+  (reduce #'(lambda (item ps)
+              (append (mapcar #'(lambda (e) (cons item e))
+                              ps)
+                      ps))
+          s
+          :from-end t
+          :initial-value '(())))

Task/Power-set/Common-Lisp/power-set-2.lisp

@@ -0,0 +1,6 @@
+(defun powerset (l)
+  (if (null l)
+      (list nil)
+      (let ((prev (powerset (cdr l))))
+	(append (mapcar #'(lambda (elt) (cons (car l) elt)) prev)
+		prev))))

Task/Power-set/Common-Lisp/power-set-3.lisp

@@ -0,0 +1,3 @@
+(defun powerset (xs)
+  (loop for i below (expt 2 (length xs)) collect
+       (loop for j below i for x in xs if (logbitp j i) collect x)))