Power set: Difference between revisions

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 =={{header|Nim}}==
 <lang nim>import sets, hashes
 proc hash(x: HashSet[int]): Hash =
   var h = 0
   for i in x: h = h !& hash(i)
   result = !$h
-proc powerset[T](inset: HashSet[T]): auto =
+proc powerset[T](inset: HashSet[T]): HashSet[HashSet[T]] =
-  result = toSet([initSet[T]()])
+  result.incl(initHashSet[T]())  # Initialized with empty set.
+  for val in inset:
+    let previous = result
-  for i in inset:
-    var tmp = result
+    for aSet in previous:
-    for j in result:
+      var newSet = aSet
-      var k = j
+      newSet.incl(val)
-      k.incl(i)
+      result.incl(newSet)
-      tmp.incl(k)
+echo powerset([1,2,3,4].toHashSet())</lang>
-    result = tmp
-echo powerset(toSet([1,2,3,4]))</lang>
 =={{header|Objective-C}}==