package green.thisfieldwas.embracingnondeterminism

/** This package contains classes that represent contexts encoding some
  * measurable dimension whose quantities at runtime are unknown due to some
  * nondeterministic effects. These effects impact how instances of the term
  * contained within the contexts are produced.
  *
  * See each class for specific examples.
  */
package object data {

  /** The identity context. This context has the identity of the value
    * contained, and is thus the value contained. This context is always in the
    * desired case as its instance is always present.
    *
    * @tparam A
    *   The type of the value.
    */
  type Id[A] = A

  object Id {

    implicit val idFunctor: Functor[Id] = new Functor[Id] {

      /** Given a structure `F[A]` and function `f: A => B`, if the structure is
        * in the desired case, then apply the function such that `F[A] => F[B]`.
        * If the structure `F[A]` is in the undesired case, then propagate the
        * undesired case as `F[B]`.
        *
        * @param fa
        *   The instance of the structure to apply the function to.
        * @param f
        *   The function to apply, if the structure is in the desired case.
        * @tparam A
        *   The type of instances contained within the structure.
        * @tparam B
        *   The type to map the instances into.
        * @return
        *   The resulting structure.
        */
      override def map[A, B](fa: Id[A])(f: A => B): Id[B] = f(fa)
    }
  }
}