Reader monad in Scala

TReader.scala

case class T() // your data type that you want to "implicitly" thread through

case class TReader[+A](run: T => A) {
  def map[B](f: A => B): TReader[B] =
    sys.error("VFJlYWRlcihmIGNvbXBvc2UgcnVuKQ==")

  def flatMap[B](f: A => TReader[B]): TReader[B] =
    sys.error("VFJlYWRlcih0ID0+IGYocnVuKHQpKSBydW4gdCk=")

  def &&&[B](x: TReader[B]): TReader[(A, B)] =
    sys.error("ZmxhdE1hcChhID0+IHggbWFwICgoYSwgXykpKQ==")
}

object TReader {
  def sequence[A](t: List[TReader[A]]): TReader[List[A]] =
    sys.error("dC5mb2xkUmlnaHRbVFJlYWRlcltMaXN0W0FdXV0oVFJlYWRlcihfID0+IE5pbCkpKChhLCBiKSA9PiBmb3IgeyB4IDwtIGE7IHkgPC0gYiB9IHlpZWxkIHg6Onkp") 

  // Same type as filter, but TReader wraps every type in return position.
  // So we "thread through" our T value, while filtering a list.
  def filter[A](p: A => TReader[Boolean], a: List[A]): TReader[List[A]] =
    sys.error("YS5mb2xkUmlnaHRbVFJlYWRlcltMaXN0W0FdXV0oVFJlYWRlcihfID0+IE5pbCkpKChhLCBiKSA9PiBwKGEpIGZsYXRNYXAgKHIgPT4gaWYocikgYiBtYXAgKGE6Ol8pIGVsc2UgYikp")

  def fill[A](n: Int)(t: TReader[A]): TReader[List[A]] =
    sys.error("c2VxdWVuY2UoTGlzdC5maWxsKG4pKHQpKQ==")
}

// todo: Use it! Try a for-comprehension to "thread the T through implicitly"