patterns.swift

indirect enum Type: CustomStringConvertible {
  case Int
  case Fun(Type, Type)

  var isFun: Bool {
    switch self {
      case .Fun: return true
      case _: return false
    }
  }

  var description: String {
    switch self {
      case .Int: return "int"
      case .Fun(let p, let r) where p.isFun: return "(\(p)) -> \(r)"
      case .Fun(let p, let r): return "(\(p) -> \(r))"
    }
  }
}