struct KV(K, V, string keyName = "key", string valueName = "value") {
  mixin("K " ~ keyName ~ ";");
  mixin("V " ~ valueName ~ ";");

  bool opEquals()(auto const ref KV s) const {
    return mixin(keyName) == mixin("s." ~ keyName);
  }

  int opCmp(const ref KV s) const {
    return cmp(mixin(keyName), mixin("s." ~ keyName));
  }
}

auto createMap(K, V, alias less = "a < b", alias keyName = "key", alias valueName = "value", bool allowDups = false)() {
  return new RedBlackTree!(KV!(K, V, keyName, valueName), less, allowDups);
}

unittest {
  auto map = createMap!(string, int, "a < b", "str", "bob");
  map.stableInsert(map.Elem("hello", 5));
  map.stableInsert(map.Elem("zbd", 3));
  map.stableInsert(map.Elem("abc", 9));

  auto rng = map[];
  assert(rng.front == map.Elem("abc", 9));
  assert(rng.front.str == "abc");
  assert(rng.front.bob == 9);
}