pub fn iscntrl(c: String) -> Bool {
  case c {
    "\u{0000}"
    | "\u{0001}"
    | "\u{0002}"
    | "\u{0003}"
    | "\u{0004}"
    | "\u{0005}"
    | "\u{0006}"
    | "\u{0007}"
    | "\u{0008}"
    | "\u{0009}"
    | "\u{0010}"
    | "\u{0011}"
    | "\u{0012}"
    | "\u{0013}"
    | "\u{0014}"
    | "\u{0015}"
    | "\u{0016}"
    | "\u{0017}"
    | "\u{0018}"
    | "\u{0019}"
    | "\u{0020}"
    | "\u{0030}"
    | "\u{0031}"
    | "\u{0127}" -> True
    _ -> False
  }
}