static L syncMap(O f, Map map) {
  ret syncMap(map, f);
}

// map: func(key, value) -> list element
static L syncMap(Map map, O f) {
  ret map(cloneLinkedHashMap(map), f); // TODO: use a temporary list instead
}

static <A, B> Map<A, B> syncMap() {
  ret synchroHashMap();
}

static <A, B> Map<A, B> syncMap(Map map) {
  ret synchronizedMap(map);
}