tasks a-s

Task/Permutations/Qi/permutations.qi

@@ -0,0 +1,19 @@
+(define insert
+  L      0 E -> [E|L]
+  [L|Ls] N E -> [L|(insert Ls (- N 1) E)])
+
+(define seq
+  Start Start -> [Start]
+  Start End   -> [Start|(seq (+ Start 1) End)])
+
+(define append-lists
+  []    -> []
+  [A|B] -> (append A (append-lists B)))
+
+(define permutate
+  []    -> [[]]
+  [H|T] -> (append-lists (map (/. P
+                                  (map (/. N
+                                           (insert P N H))
+                                       (seq 0 (length P))))
+                              (permute T))))