scalaz.WriterT.scala Maven / Gradle / Ivy
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package scalaz
import Id._
final case class WriterT[F[_], W, A](run: F[(W, A)]) { self =>
import WriterT._
def off: UnwriterT[F, W, A] =
UnwriterT(run)
/** alias for `off` */
def unary_- : UnwriterT[F, W, A] =
UnwriterT(run)
def mapValue[X, B](f: ((W, A)) => (X, B))(implicit F: Functor[F]): WriterT[F, X, B] =
writerT(F.map(run)(f))
def mapWritten[X](f: W => X)(implicit F: Functor[F]): WriterT[F, X, A] =
mapValue(wa => (f(wa._1), wa._2))
def written(implicit F: Functor[F]): F[W] =
F.map(run)(_._1)
def value(implicit F: Functor[F]): F[A] =
F.map(run)(_._2)
def swap(implicit F: Functor[F]): WriterT[F, A, W] =
mapValue(wa => (wa._2, wa._1))
def :++>(w: => W)(implicit F: Functor[F], W: Semigroup[W]): WriterT[F, W, A] =
mapWritten(W.append(_, w))
def :++>>(f: A => W)(implicit F: Functor[F], W: Semigroup[W]): WriterT[F, W, A] =
mapValue(wa => (W.append(wa._1, f(wa._2)), wa._2))
def <++:(w: => W)(implicit F: Functor[F], W: Semigroup[W]): WriterT[F, W, A] =
mapWritten(W.append(w, _))
def <<++:(f: A => W)(implicit F: Functor[F], s: Semigroup[W]): WriterT[F, W, A] =
mapValue(wa => (s.append(f(wa._2), wa._1), wa._2))
def reset(implicit Z: Monoid[W], F: Functor[F]): WriterT[F, W, A] =
mapWritten(_ => Z.zero)
def map[B](f: A => B)(implicit F: Functor[F]): WriterT[F, W, B] =
writerT(F.map(run)(wa => (wa._1, f(wa._2))))
@deprecated("Each/foreach is deprecated", "7.1")
def foreach[B](f: A => Unit)(implicit E: Each[F]): Unit =
E.each(run)(wa => f(wa._2))
def ap[B](f: => WriterT[F, W, A => B])(implicit F: Apply[F], W: Semigroup[W]): WriterT[F, W, B] = writerT {
F.apply2(f.run, run) {
case ((w1, fab), (w2, a)) => (W.append(w1, w2), fab(a))
}
}
def flatMap[B](f: A => WriterT[F, W, B])(implicit F: Bind[F], s: Semigroup[W]): WriterT[F, W, B] =
writerT(F.bind(run){wa =>
val z = f(wa._2).run
F.map(z)(wb => (s.append(wa._1, wb._1), wb._2))
})
def traverse[G[_], B](f: A => G[B])(implicit G: Applicative[G], F: Traverse[F]): G[WriterT[F, W, B]] = {
G.map(F.traverse(run){
case (w, a) => G.map(f(a))(b => (w, b))
})(WriterT(_))
}
def foldRight[B](z: => B)(f: (A, => B) => B)(implicit F: Foldable[F]) =
F.foldr(run, z) { a => b =>
f(a._2, b)
}
def bimap[C, D](f: W => C, g: A => D)(implicit F: Functor[F]) =
writerT[F, C, D](F.map(run)({
case (a, b) => (f(a), g(b))
}))
def leftMap[C](f: W => C)(implicit F: Functor[F]): WriterT[F, C, A] =
bimap(f, identity)
def bitraverse[G[_], C, D](f: W => G[C], g: A => G[D])(implicit G: Applicative[G], F: Traverse[F]) =
G.map(F.traverse[G, (W, A), (C, D)](run) {
case (a, b) => G.apply2(f(a), g(b))((_, _))
})(writerT(_))
def rwst[R, S](implicit F: Functor[F]): ReaderWriterStateT[F, R, W, S, A] = ReaderWriterStateT(
(r, s) => F.map(self.run) {
case (w, a) => (w, a, s)
}
)
def wpoint[G[_]](implicit F: Functor[F], P: Applicative[G]): WriterT[F, G[W], A] =
writerT(F.map(self.run) {
case (w, a) => (P.point(w), a)
})
def colocal[X](f: W => X)(implicit F: Functor[F]): WriterT[F, X, A] = mapWritten(f)
}
object WriterT extends WriterTInstances with WriterTFunctions
sealed abstract class WriterTInstances12 {
implicit def writerFunctor[W]: Functor[({type λ[α]=Writer[W, α]})#λ] = new WriterTFunctor[Id, W] {
implicit def F = idInstance
}
}
sealed abstract class WriterTInstances11 extends WriterTInstances12 {
implicit def writerTFunctor[F[_], W](implicit F0: Functor[F]): Functor[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTFunctor[F, W] {
implicit def F = F0
}
}
sealed abstract class WriterTInstances10 extends WriterTInstances11 {
implicit def writerApply[W](implicit W0: Semigroup[W]): Apply[({type λ[α]=Writer[W, α]})#λ] = new WriterTApply[Id, W] {
implicit def F = idInstance
implicit def W = W0
}
}
sealed abstract class WriterTInstances9 extends WriterTInstances10 {
implicit def writerTApply[F[_], W](implicit W0: Semigroup[W], F0: Apply[F]): Apply[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTApply[F, W] {
implicit def F = F0
implicit def W = W0
}
}
sealed abstract class WriterTInstances8 extends WriterTInstances9 {
implicit def writerApplicative[W](implicit W0: Monoid[W]): Applicative[({type λ[α]=Writer[W, α]})#λ] = new WriterTApplicative[Id, W] {
implicit def F = idInstance
implicit def W = W0
}
}
sealed abstract class WriterTInstances7 extends WriterTInstances8 {
implicit def writerTApplicative[F[_], W](implicit W0: Monoid[W], F0: Applicative[F]): Applicative[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTApplicative[F, W] {
implicit def F = F0
implicit def W = W0
}
}
sealed abstract class WriterTInstances6 extends WriterTInstances7 {
implicit def writerMonad[W](implicit W0: Monoid[W]): Monad[({type λ[α]=Writer[W, α]})#λ] = new WriterTMonad[Id, W] {
implicit def F = idInstance
implicit def W = W0
}
}
sealed abstract class WriterTInstance5 extends WriterTInstances6 {
implicit def writerTMonad[F[_], W](implicit W0: Monoid[W], F0: Monad[F]): Monad[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTMonad[F, W] {
implicit def F = F0
implicit def W = W0
}
}
sealed abstract class WriterTInstances4 extends WriterTInstance5 {
implicit def writerFoldable[W]: Foldable[({type λ[α]=Writer[W, α]})#λ] = new WriterTFoldable[Id, W] {
implicit def F = idInstance
}
implicit def writerEqual[W, A](implicit E: Equal[(W, A)]): Equal[Writer[W, A]] = E.contramap((_: Writer[W, A]).run)
}
sealed abstract class WriterTInstances3 extends WriterTInstances4 {
implicit def writerTBifunctor[F[_]](implicit F0: Functor[F]): Bifunctor[({type λ[α, β]=WriterT[F, α, β]})#λ] = new WriterTBifunctor[F] {
implicit def F = F0
}
implicit def writerTFoldable[F[_], W](implicit F0: Foldable[F]): Foldable[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTFoldable[F, W] {
implicit def F = F0
}
implicit def writerTEqual[F[_], W, A](implicit E: Equal[F[(W, A)]]): Equal[WriterT[F, W, A]] = E.contramap((_: WriterT[F, W, A]).run)
}
sealed abstract class WriterTInstances2 extends WriterTInstances3 {
implicit def writerComonad[W]: Comonad[({type λ[α]=Writer[W, α]})#λ] = new WriterComonad[W] {
implicit def F = implicitly
}
}
sealed abstract class WriterTInstances1 extends WriterTInstances2 {
implicit val writerBitraverse: Bitraverse[Writer] = new WriterTBitraverse[Id] {
implicit def F = idInstance
}
implicit def writerTraverse[W]: Traverse[({type λ[α]=Writer[W, α]})#λ] = new WriterTTraverse[Id, W] {
implicit def F = idInstance
}
@deprecated("Each/foreach is deprecated", "7.1")
implicit def writerEach[W]: Each[({type λ[α]=Writer[W, α]})#λ] = new WriterTEach[Id, W] {
implicit def F = idInstance
}
}
sealed abstract class WriterTInstances0 extends WriterTInstances1 {
implicit def writerTBitraverse[F[_]](implicit F0: Traverse[F]): Bitraverse[({type λ[α, β]=WriterT[F, α, β]})#λ] = new WriterTBitraverse[F] {
implicit def F = F0
}
implicit def writerTTraverse[F[_], W](implicit F0: Traverse[F]): Traverse[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTTraverse[F, W] {
implicit def F = F0
}
@deprecated("Index is deprecated, use Foldable instead", "7.1")
implicit def writerIndex[W]: Index[({type λ[α]=Writer[W, α]})#λ] = new WriterIndex[W] {
}
@deprecated("Each/foreach is deprecated", "7.1")
implicit def writerTEach[F[_], W](implicit F0: Each[F]): Each[({type λ[α]=WriterT[F, W, α]})#λ] = new WriterTEach[F, W] {
implicit def F = F0
}
}
sealed abstract class WriterTInstances extends WriterTInstances0 {
implicit def writerTMonadListen[F[_], W](implicit F0: Monad[F], W0: Monoid[W]): MonadListen[({type λ[α, β] = WriterT[F, α, β]})#λ, W] = new WriterTMonadListen[F, W] {
implicit def F = F0
implicit def W = W0
}
implicit def writerTHoist[W](implicit W0: Monoid[W]): Hoist[({type λ[α[_], β] = WriterT[α, W, β]})#λ] = new WriterTHoist[W] {
implicit def W = W0
}
}
trait WriterTFunctions {
def writerT[F[_], W, A](v: F[(W, A)]): WriterT[F, W, A] = WriterT(v)
def writer[W, A](v: (W, A)): Writer[W, A] =
writerT[Id, W, A](v)
def tell[W](w: W): Writer[W, Unit] = writer(w -> ())
def put[F[_], W, A](value: F[A])(w: W)(implicit F: Functor[F]): WriterT[F, W, A] =
WriterT(F.map(value)(a => (w, a)))
/** Puts the written value that is produced by applying the given function into a writer transformer and associates with `value` */
def putWith[F[_], W, A](value: F[A])(w: A => W)(implicit F: Functor[F]): WriterT[F, W, A] =
WriterT(F.map(value)(a => (w(a), a)))
}
//
// Type class implementation traits
//
import WriterT.writerT
private trait WriterTFunctor[F[_], W] extends Functor[({type λ[α]=WriterT[F, W, α]})#λ] {
implicit def F: Functor[F]
override def map[A, B](fa: WriterT[F, W, A])(f: A => B) = fa map f
}
private trait WriterTApply[F[_], W] extends Apply[({type λ[α]=WriterT[F, W, α]})#λ] with WriterTFunctor[F, W] {
implicit def F: Apply[F]
implicit def W: Semigroup[W]
override def ap[A, B](fa: => WriterT[F, W, A])(f: => WriterT[F, W, A => B]) = fa ap f
}
private trait WriterTApplicative[F[_], W] extends Applicative[({type λ[α]=WriterT[F, W, α]})#λ] with WriterTApply[F, W] {
implicit def F: Applicative[F]
implicit def W: Monoid[W]
def point[A](a: => A) = writerT(F.point((W.zero, a)))
}
private trait WriterTEach[F[_], W] extends Each[({type λ[α]=WriterT[F, W, α]})#λ] {
implicit def F: Each[F]
def each[A](fa: WriterT[F, W, A])(f: A => Unit) = fa foreach f
}
// TODO does Index it make sense for F other than Id?
private trait WriterIndex[W] extends Index[({type λ[α]=Writer[W, α]})#λ] {
def index[A](fa: Writer[W, A], i: Int) = if(i == 0) Some(fa.value) else None
}
private trait WriterTMonad[F[_], W] extends Monad[({type λ[α]=WriterT[F, W, α]})#λ] with WriterTApplicative[F, W] {
implicit def F: Monad[F]
def bind[A, B](fa: WriterT[F, W, A])(f: A => WriterT[F, W, B]) = fa flatMap f
}
private trait WriterTFoldable[F[_], W] extends Foldable.FromFoldr[({type λ[α]=WriterT[F, W, α]})#λ] {
implicit def F: Foldable[F]
override def foldRight[A, B](fa: WriterT[F, W, A], z: => B)(f: (A, => B) => B) = fa.foldRight(z)(f)
}
private trait WriterTTraverse[F[_], W] extends Traverse[({type λ[α]=WriterT[F, W, α]})#λ] with WriterTFoldable[F, W] {
implicit def F: Traverse[F]
def traverseImpl[G[_]: Applicative, A, B](fa: WriterT[F, W, A])(f: A => G[B]) = fa traverse f
}
private trait WriterTBifunctor[F[_]] extends Bifunctor[({type λ[α, β]=WriterT[F, α, β]})#λ] {
implicit def F: Functor[F]
override def bimap[A, B, C, D](fab: WriterT[F, A, B])(f: A => C, g: B => D) =
fab.bimap(f, g)
}
private trait WriterTBitraverse[F[_]] extends Bitraverse[({type λ[α, β]=WriterT[F, α, β]})#λ] with WriterTBifunctor[F] {
implicit def F: Traverse[F]
def bitraverseImpl[G[_]: Applicative, A, B, C, D](fab: WriterT[F, A, B])(f: A => G[C], g: B => G[D]) =
fab.bitraverse(f, g)
}
private trait WriterComonad[W] extends Comonad[({type λ[α] = Writer[W, α]})#λ] with WriterTFunctor[Id, W] {
def copoint[A](p: Writer[W, A]): A = p.value
override def cojoin[A](fa: Writer[W, A]): Writer[W, Writer[W, A]] =
Writer(fa.written, fa)
override def cobind[A, B](fa: Writer[W, A])(f: (Writer[W, A]) => B): Writer[W, B] =
Writer(fa.written, f(fa))
}
private trait WriterTHoist[W] extends Hoist[({type λ[α[_], β] = WriterT[α, W, β]})#λ] {
def liftM[M[_], B](mb: M[B])(implicit M: Monad[M]): WriterT[M, W, B] =
WriterT(M.map(mb)((W.zero, _)))
implicit def W: Monoid[W]
implicit def apply[M[_]: Monad]: Monad[({type λ[α]=WriterT[M, W, α]})#λ] = WriterT.writerTMonad
def hoist[M[_]: Monad, N[_]](f: M ~> N) = new (({type λ[α]=WriterT[M, W, α]})#λ ~> ({type λ[α]=WriterT[N, W, α]})#λ) {
def apply[A](fa: WriterT[M, W, A]) = WriterT(f(fa.run))
}
}
private trait WriterTMonadListen[F[_], W] extends MonadListen[({type λ[α, β] = WriterT[F, α, β]})#λ, W] with WriterTMonad[F, W] {
implicit def F: Monad[F]
implicit def W: Monoid[W]
def writer[A](w: W, v: A): WriterT[F, W, A] = WriterT.writerT(F.point((w, v)))
def listen[A](fa: WriterT[F, W, A]): WriterT[F, W, (A, W)] =
WriterT(F.bind(fa.run){ case (w, a) => F.point((w, (a, w))) })
}
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