diff --git a/tests/bench/rbmap.swift b/tests/bench/rbmap.swift
new file mode 100644
index 0000000000..eb869423f6
--- /dev/null
+++ b/tests/bench/rbmap.swift
@@ -0,0 +1,128 @@
+enum Color {
+  case Red
+  case Black
+}
+
+indirect enum Tree {
+  case Leaf
+  case Node(Color, Tree, UInt64, Bool, Tree)
+}
+
+func balance1(_ kv : UInt64, _ vv : Bool, _ t : Tree, _ n : Tree) -> Tree {
+  switch n {
+  case let .Node(_, .Node(.Red, l, kx, vx, r1), ky, vy, r2):
+    return .Node(.Red, .Node(.Black, l, kx, vx, r1), ky, vy, .Node(.Black, r2, kv, vv, t))
+  case let .Node(_, l1, ky, vy, .Node(.Red, l2, kx, vx, r)):
+    return .Node(.Red, .Node(.Black, l1, ky, vy, l2), kx, vx, .Node(.Black, r, kv, vv, t))
+  case let .Node(_, l, ky, vy, r):
+    return .Node(.Black, .Node(.Red, l, ky, vy, r), kv, vv, t)
+  default:
+    return .Leaf
+  }
+}
+
+func balance2(_ t : Tree, _ kv : UInt64, _ vv : Bool, _ n : Tree) -> Tree {
+  switch n {
+  case let .Node(_, .Node(.Red, l, kx1, vx1, r1), ky, vy, r2):
+    return .Node(.Red, .Node(.Black, t, kv, vv, l), kx1, vx1, .Node(.Black, r1, ky, vy, r2))
+  case let .Node(_, l1, ky, vy, .Node(.Red, l2, kx2, vx2, r2)):
+    return .Node(.Red, .Node(.Black, t, kv, vv, l1), ky, vy, .Node(.Black, l2, kx2, vx2, r2))
+  case let .Node (_, l, ky, vy, r):
+    return .Node(.Black, t, kv, vv, .Node(.Red, l, ky, vy, r))
+  default:
+    return .Leaf
+  }
+}
+
+func is_red (_ t : Tree) -> Bool {
+  switch t {
+  case .Node(.Red, _, _, _, _):
+    return true
+  default:
+    return false
+  }
+}
+
+func ins(_ t : Tree, _ kx : UInt64, _ vx : Bool) -> Tree {
+  switch t {
+  case .Leaf:
+    return .Node(.Red, .Leaf, kx, vx, .Leaf)
+  case let .Node(.Red, a, ky, vy, b):
+    if kx < ky {
+      return .Node(.Red, ins(a, kx, vx), ky, vy, b)
+    } else if ky == kx {
+      return .Node(.Red, a, kx, vx, b)
+    } else {
+      return .Node(.Red, a, ky, vy, ins(b, kx, vx))
+    }
+  case let .Node(.Black, a, ky, vy, b):
+   if kx < ky {
+    if is_red(a) {
+      return balance1(ky, vy, b, ins(a, kx, vx))
+    } else {
+      return .Node(.Black, ins(a, kx, vx), ky, vy, b)
+    }
+   } else if kx == ky {
+     return .Node(.Black, a, kx, vx, b)
+   } else {
+     if is_red(b) {
+       return balance2(a, ky, vy, ins(b, kx, vx))
+     } else {
+       return .Node(.Black, a, ky, vy, ins(b, kx, vx))
+     }
+   }
+  }
+}
+
+func set_black (_ n : Tree) -> Tree {
+  switch n {
+  case let .Node (_, l, k, v, r):
+    return .Node (.Black, l, k, v, r)
+  default:
+    return n
+  }
+}
+
+func insert (_ t : Tree, _ k : UInt64, _ v : Bool) -> Tree {
+ if is_red(t) {
+   return set_black(ins(t, k, v))
+ } else {
+   return ins(t, k, v)
+ }
+}
+
+func fold (_ f : (_ k : UInt64, _ v : Bool, _ d : UInt64) -> UInt64, _ n : Tree, _ d : UInt64) -> UInt64 {
+  switch n {
+  case .Leaf:
+    return d
+  case let .Node(_, l, k, v, r):
+    return fold(f, r, f(k, v, fold(f, l, d)))
+  }
+}
+
+func mk_map (_ n : UInt64) -> Tree {
+  var i = n
+  var m : Tree = .Leaf
+  while i > 0 {
+    i = i - 1
+    m = insert(m, i, (i%10 == 0))
+  }
+  return m
+}
+
+func aux (_ k : UInt64, _ v : Bool, _ r : UInt64) -> UInt64 {
+  if v {
+    return r + 1
+  } else {
+    return r
+  }
+}
+
+if CommandLine.arguments.count != 2 {
+  print("Incorrect number of arguments")
+} else {
+  let num  = UInt64(CommandLine.arguments[1])
+  let m = mk_map(num!)
+  let v = fold(aux, m, 0)
+  print(v)
+}