tasks a-s

Task/Power-set/Erlang/power-set-1.erl

@@ -0,0 +1,5 @@
+powerset(Lst) ->
+    N = length(Lst),
+    Max = trunc(math:pow(2,N)),
+    [[lists:nth(Pos+1,Lst) || Pos <- lists:seq(0,N-1), I band (1 bsl Pos) =/= 0]
+      || I <- lists:seq(0,Max-1)].

Task/Power-set/Erlang/power-set-2.erl

@@ -0,0 +1,3 @@
+powerset([]) -> [[]];
+powerset([H|T]) -> PT = powerset(T),
+  [ [H|X] || X <- PT ] ++ PT.

Task/Power-set/Erlang/power-set-3.erl

@@ -0,0 +1,6 @@
+powerset([]) -> [[]];
+powerset([H|T]) -> PT = powerset(T),
+  powerset(H, PT, PT).
+
+powerset(_, [], Acc) -> Acc;
+powerset(X, [H|T], Acc) -> powerset(X, T, [[X|H]|Acc]).