Dependent Function1

depfun.scala

trait DepFunction1[T]{ self =>
  type R
  
  def apply(t: T): R
  
  def andThen(dep: DepFunction1[R]): Aux[T, dep.R] = new DepFunction1[T]{
    type R = dep.R
    
    def apply(t: T) = dep(self(t))
  }
  
  def compose[A](dep: Aux[A, T]): Aux[A, R] = dep andThen self
  
  def andThen[A](f: R => A): Aux[T, A] = new DepFunction1[T]{
    type R = A
    
    def apply(t: T) = f(self(t))
  }
  
  def compose[A](f: A => T): Aux[A, R] = new DepFunction1[A]{
    type R = self.R
    
    def apply(a: A) = self(f(a))
  }
}

object DepFunction1{
  type Aux[T, R0] = DepFunction1[T]{ type R = R0 }
}