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Task/Power-set/Nim/power-set.nim

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+import sets, hashes
+
+proc hash(x): THash =
+  var h = 0
+  for i in x: h = h !& hash(i)
+  result = !$h
+
+proc powerset[T](inset: HashSet[T]): auto =
+  result = toSet([initSet[T]()])
+
+  for i in inset:
+    var tmp = result
+    for j in result:
+      var k = j
+      k.incl(i)
+      tmp.incl(k)
+    result = tmp
+
+echo powerset(toSet([1,2,3,4]))