monocle.function.Snoc.scala Maven / Gradle / Ivy

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package monocle.function

import monocle.{Optional, Prism}
import monocle.std.tuple2._

import scala.annotation.implicitNotFound
import scalaz.Maybe


@implicitNotFound("Could not find an instance of Snoc[${S},${A}], please check Monocle instance location policy to " +
  "find out which import is necessary")
trait Snoc[S, A] {

  def snoc: Prism[S, (S, A)]

  def initMaybe: Optional[S, S] = snoc composeLens first
  def lastMaybe: Optional[S, A] = snoc composeLens second

}

object Snoc extends SnocFunctions

trait SnocFunctions {
  final def snoc[S, A](implicit ev: Snoc[S, A]): Prism[S, (S, A)] = ev.snoc

  final def initMaybe[S, A](implicit ev: Snoc[S, A]): Optional[S, S] = ev.initMaybe
  final def lastMaybe[S, A](implicit ev: Snoc[S, A]): Optional[S, A] = ev.lastMaybe

  /** append an element to the end */
  final def _snoc[S, A](init: S, last: A)(implicit ev: Snoc[S, A]): S =
    ev.snoc.reverseGet((init, last))

  /** deconstruct an S between its init and last */
  final def _unsnoc[S, A](s: S)(implicit ev: Snoc[S, A]): Maybe[(S, A)] =
    ev.snoc.getMaybe(s)
}