fixes #3221

tests/iter/tcomplex_openarray.nim

@@ -0,0 +1,33 @@
+
+# bug #3221
+
+import algorithm, math, sequtils
+
+
+iterator permutations[T](ys: openarray[T]): seq[T] =
+  var
+    d = 1
+    c = newSeq[int](ys.len)
+    xs = newSeq[T](ys.len)
+  for i, y in ys: xs[i] = y
+  yield xs
+  block outer:
+    while true:
+      while d > 1:
+        dec d
+        c[d] = 0
+      while c[d] >= d:
+        inc d
+        if d >= ys.len: break outer
+      let i = if (d and 1) == 1: c[d] else: 0
+      swap xs[i], xs[d]
+      yield xs
+      inc c[d]
+
+proc dig_vectors(): void =
+  var v_nums: seq[int]
+  v_nums = newSeq[int](1)
+  for perm in permutations(toSeq(0 .. 1)):
+    v_nums[0] = 1
+
+dig_vectors()