September 2017 Update

Task/Power-set/Jq/power-set-1.jq

@@ -0,0 +1,3 @@
+def powerset:
+  reduce .[] as $i ([[]];
+     reduce .[] as $r (.; . + [$r + [$i]]));

Task/Power-set/Jq/power-set-2.jq

@@ -0,0 +1,7 @@
+# The power set of the empty set:
+  [] | powerset
+  # => [[]]
+
+# The power set of the set which contains only the empty set:
+  [ [] ] | powerset
+  # => [[],[[]]]

Task/Power-set/Jq/power-set-3.jq

@@ -0,0 +1,6 @@
+def powerset:
+  if length == 0 then [[]]
+  else .[0] as $first
+    | (.[1:] | powerset)
+    | map([$first] + . ) + .
+  end;