Simplified Iteratees using trait modules

iteratees.scala

// Note:  "Context" is the Monad through which these classes are threaded.  There also exists a type alias for the error channel between
// consumers and producers so that Consumers can be random-access.   That code lives in the "randomaccess" universe for Iteratees, which is
// an extension of the sequential "nio" universe.

// Note: I don't have a ConsumerT, ProducerT, or StreamConverterT yet.
trait Consumer[I,O] {
    /** Fold takes a function that matches the current state of this Consumer and produces a result. */
    def fold[R](f: ConsumerState[I,O] => Context[R]): Context[R]
}

trait Producer[A] {
  /** Feeds values from this producer into a consumer. */
  def into[O](c: Consumer[A, O]): Consumer[A, O]
}

trait StreamConversion[I,I2] {
  def apply[O](i: Consumer[I2,O]): Consumer[I, Consumer[I2, O]]
  def convert[O](i: Consumer[I2, O])(implicit ev0: Empty[I]): Consumer[I, O] = apply(i).join
}