trait MonadError[F[_], E] extends ApplicativeError[F, E] with Monad[F]
A monad that also allows you to raise and or handle an error value.
This type class allows one to abstract over error-handling monads.
- Source
- MonadError.scala
- Grouped
- Alphabetic
- By Inheritance
- MonadError
- Monad
- FlatMap
- ApplicativeError
- Applicative
- InvariantMonoidal
- Apply
- ApplyArityFunctions
- InvariantSemigroupal
- Semigroupal
- Functor
- Invariant
- Serializable
- Serializable
- AnyRef
- Any
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- Public
- All
Abstract Value Members
-
abstract
def
flatMap[A, B](fa: F[A])(f: (A) ⇒ F[B]): F[B]
- Definition Classes
- FlatMap
-
abstract
def
handleErrorWith[A](fa: F[A])(f: (E) ⇒ F[A]): F[A]
Handle any error, potentially recovering from it, by mapping it to an
F[A]
value.Handle any error, potentially recovering from it, by mapping it to an
F[A]
value.- Definition Classes
- ApplicativeError
- See also
handleError to handle any error by simply mapping it to an
A
value instead of anF[A]
.recoverWith to recover from only certain errors.
-
abstract
def
pure[A](x: A): F[A]
pure
lifts any value into the Applicative Functor.pure
lifts any value into the Applicative Functor.Example:
scala> import cats.implicits._ scala> Applicative[Option].pure(10) res0: Option[Int] = Some(10)
- Definition Classes
- Applicative
-
abstract
def
raiseError[A](e: E): F[A]
Lift an error into the
F
context.Lift an error into the
F
context.Example:
scala> import cats.implicits._ // integer-rounded division scala> def divide[F[_]](dividend: Int, divisor: Int)(implicit F: ApplicativeError[F, String]): F[Int] = | if (divisor === 0) F.raiseError("division by zero") | else F.pure(dividend / divisor) scala> type ErrorOr[A] = Either[String, A] scala> divide[ErrorOr](6, 3) res0: ErrorOr[Int] = Right(2) scala> divide[ErrorOr](6, 0) res1: ErrorOr[Int] = Left(division by zero)
- Definition Classes
- ApplicativeError
-
abstract
def
tailRecM[A, B](a: A)(f: (A) ⇒ F[Either[A, B]]): F[B]
Keeps calling
f
until ascala.util.Right[B]
is returned.Keeps calling
f
until ascala.util.Right[B]
is returned.Based on Phil Freeman's Stack Safety for Free.
Implementations of this method should use constant stack space relative to
f
.- Definition Classes
- FlatMap
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
-
final
def
*>[A, B](fa: F[A])(fb: F[B]): F[B]
Alias for productR.
-
final
def
<*[A, B](fa: F[A])(fb: F[B]): F[A]
Alias for productL.
-
final
def
<*>[A, B](ff: F[(A) ⇒ B])(fa: F[A]): F[B]
Alias for ap.
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
adaptError[A](fa: F[A])(pf: PartialFunction[E, E]): F[A]
Transform certain errors using
pf
and rethrow them.Transform certain errors using
pf
and rethrow them. Non matching errors and successful values are not affected by this function.Example:
scala> import cats._, implicits._ scala> def pf: PartialFunction[String, String] = { case "error" => "ERROR" } scala> ApplicativeError[Either[String, *], String].adaptError("error".asLeft[Int])(pf) res0: Either[String,Int] = Left(ERROR) scala> ApplicativeError[Either[String, *], String].adaptError("err".asLeft[Int])(pf) res1: Either[String,Int] = Left(err) scala> ApplicativeError[Either[String, *], String].adaptError(1.asRight[String])(pf) res2: Either[String,Int] = Right(1)
The same function is available in
ApplicativeErrorOps
asadaptErr
- it cannot have the same name because this would result in ambiguous implicits due toadaptError
having originally been included in theMonadError
API and syntax.- Definition Classes
- MonadError → ApplicativeError
-
def
ap[A, B](ff: F[(A) ⇒ B])(fa: F[A]): F[B]
Given a value and a function in the Apply context, applies the function to the value.
Given a value and a function in the Apply context, applies the function to the value.
Example:
scala> import cats.implicits._ scala> val someF: Option[Int => Long] = Some(_.toLong + 1L) scala> val noneF: Option[Int => Long] = None scala> val someInt: Option[Int] = Some(3) scala> val noneInt: Option[Int] = None scala> Apply[Option].ap(someF)(someInt) res0: Option[Long] = Some(4) scala> Apply[Option].ap(noneF)(someInt) res1: Option[Long] = None scala> Apply[Option].ap(someF)(noneInt) res2: Option[Long] = None scala> Apply[Option].ap(noneF)(noneInt) res3: Option[Long] = None
-
def
ap10[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap11[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap12[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap13[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap14[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap15[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap16[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap17[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap18[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap19[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap2[A, B, Z](ff: F[(A, B) ⇒ Z])(fa: F[A], fb: F[B]): F[Z]
ap2 is a binary version of ap, defined in terms of ap.
-
def
ap20[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap21[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap22[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20], f21: F[A21]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap3[A0, A1, A2, Z](f: F[(A0, A1, A2) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap4[A0, A1, A2, A3, Z](f: F[(A0, A1, A2, A3) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap5[A0, A1, A2, A3, A4, Z](f: F[(A0, A1, A2, A3, A4) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap6[A0, A1, A2, A3, A4, A5, Z](f: F[(A0, A1, A2, A3, A4, A5) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap7[A0, A1, A2, A3, A4, A5, A6, Z](f: F[(A0, A1, A2, A3, A4, A5, A6) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap8[A0, A1, A2, A3, A4, A5, A6, A7, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
ap9[A0, A1, A2, A3, A4, A5, A6, A7, A8, Z](f: F[(A0, A1, A2, A3, A4, A5, A6, A7, A8) ⇒ Z])(f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8]): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
as[A, B](fa: F[A], b: B): F[B]
Replaces the
A
value inF[A]
with the supplied value.Replaces the
A
value inF[A]
with the supplied value.Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForList scala> Functor[List].as(List(1,2,3), "hello") res0: List[String] = List(hello, hello, hello)
- Definition Classes
- Functor
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
attempt[A](fa: F[A]): F[Either[E, A]]
Handle errors by turning them into scala.util.Either values.
Handle errors by turning them into scala.util.Either values.
If there is no error, then an
scala.util.Right
value will be returned instead.All non-fatal errors should be handled by this method.
- Definition Classes
- ApplicativeError
-
def
attemptNarrow[EE <: Throwable, A](fa: F[A])(implicit tag: ClassTag[EE], ev: <:<[EE, E]): F[Either[EE, A]]
Similar to attempt, but it only handles errors of type
EE
.Similar to attempt, but it only handles errors of type
EE
.- Definition Classes
- ApplicativeError
-
def
attemptT[A](fa: F[A]): EitherT[F, E, A]
Similar to attempt, but wraps the result in a cats.data.EitherT for convenience.
Similar to attempt, but wraps the result in a cats.data.EitherT for convenience.
- Definition Classes
- ApplicativeError
-
def
attemptTap[A, B](fa: F[A])(f: (Either[E, A]) ⇒ F[B]): F[A]
Reifies the value or error of the source and performs an effect on the result, then recovers the original value or error back into
F
.Reifies the value or error of the source and performs an effect on the result, then recovers the original value or error back into
F
.Note that if the effect returned by
f
fails, the resulting effect will fail too.Alias for
fa.attempt.flatTap(f).rethrow
for convenience.Example:
scala> import cats.implicits._ scala> import scala.util.{Try, Success, Failure} scala> def checkError(result: Either[Throwable, Int]): Try[String] = result.fold(_ => Failure(new java.lang.Exception), _ => Success("success")) scala> val a: Try[Int] = Failure(new Throwable("failed")) scala> a.attemptTap(checkError) res0: scala.util.Try[Int] = Failure(java.lang.Exception) scala> val b: Try[Int] = Success(1) scala> b.attemptTap(checkError) res1: scala.util.Try[Int] = Success(1)
-
def
catchNonFatal[A](a: ⇒ A)(implicit ev: <:<[Throwable, E]): F[A]
Often E is Throwable.
Often E is Throwable. Here we try to call pure or catch and raise.
- Definition Classes
- ApplicativeError
-
def
catchNonFatalEval[A](a: Eval[A])(implicit ev: <:<[Throwable, E]): F[A]
Often E is Throwable.
Often E is Throwable. Here we try to call pure or catch and raise
- Definition Classes
- ApplicativeError
-
def
catchOnly[T >: Null <: Throwable]: CatchOnlyPartiallyApplied[T, F, E]
Evaluates the specified block, catching exceptions of the specified type.
Evaluates the specified block, catching exceptions of the specified type. Uncaught exceptions are propagated.
- Definition Classes
- ApplicativeError
-
def
clone(): AnyRef
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native() @IntrinsicCandidate()
-
def
compose[G[_]](implicit arg0: Applicative[G]): Applicative[[α]F[G[α]]]
Compose an
Applicative[F]
and anApplicative[G]
into anApplicative[λ[α => F[G[α]]]]
.Compose an
Applicative[F]
and anApplicative[G]
into anApplicative[λ[α => F[G[α]]]]
.Example:
scala> import cats.implicits._ scala> val alo = Applicative[List].compose[Option] scala> alo.pure(3) res0: List[Option[Int]] = List(Some(3)) scala> alo.product(List(None, Some(true), Some(false)), List(Some(2), None)) res1: List[Option[(Boolean, Int)]] = List(None, None, Some((true,2)), None, Some((false,2)), None)
- Definition Classes
- Applicative
-
def
compose[G[_]](implicit arg0: Apply[G]): Apply[[α]F[G[α]]]
Compose an
Apply[F]
and anApply[G]
into anApply[λ[α => F[G[α]]]]
.Compose an
Apply[F]
and anApply[G]
into anApply[λ[α => F[G[α]]]]
.Example:
scala> import cats.implicits._ scala> val alo = Apply[List].compose[Option] scala> alo.product(List(None, Some(true), Some(false)), List(Some(2), None)) res1: List[Option[(Boolean, Int)]] = List(None, None, Some((true,2)), None, Some((false,2)), None)
- Definition Classes
- Apply
-
def
compose[G[_]](implicit arg0: Functor[G]): Functor[[α]F[G[α]]]
- Definition Classes
- Functor
-
def
compose[G[_]](implicit arg0: Invariant[G]): Invariant[[α]F[G[α]]]
Compose Invariant
F[_]
andG[_]
then produceInvariant[F[G[_]]]
using theirimap
.Compose Invariant
F[_]
andG[_]
then produceInvariant[F[G[_]]]
using theirimap
.Example:
scala> import cats.implicits._ scala> import scala.concurrent.duration._ scala> val durSemigroupList: Semigroup[List[FiniteDuration]] = | Invariant[Semigroup].compose[List].imap(Semigroup[List[Long]])(Duration.fromNanos)(_.toNanos) scala> durSemigroupList.combine(List(2.seconds, 3.seconds), List(4.seconds)) res1: List[FiniteDuration] = List(2 seconds, 3 seconds, 4 seconds)
- Definition Classes
- Invariant
-
def
composeApply[G[_]](implicit arg0: Apply[G]): InvariantSemigroupal[[α]F[G[α]]]
- Definition Classes
- InvariantSemigroupal
-
def
composeContravariant[G[_]](implicit arg0: Contravariant[G]): Contravariant[[α]F[G[α]]]
Compose Invariant
F[_]
and ContravariantG[_]
then produceInvariant[F[G[_]]]
using F'simap
and G'scontramap
.Compose Invariant
F[_]
and ContravariantG[_]
then produceInvariant[F[G[_]]]
using F'simap
and G'scontramap
.Example:
scala> import cats.implicits._ scala> import scala.concurrent.duration._ scala> type ToInt[T] = T => Int scala> val durSemigroupToInt: Semigroup[ToInt[FiniteDuration]] = | Invariant[Semigroup] | .composeContravariant[ToInt] | .imap(Semigroup[ToInt[Long]])(Duration.fromNanos)(_.toNanos) // semantically equal to (2.seconds.toSeconds.toInt + 1) + (2.seconds.toSeconds.toInt * 2) = 7 scala> durSemigroupToInt.combine(_.toSeconds.toInt + 1, _.toSeconds.toInt * 2)(2.seconds) res1: Int = 7
-
def
composeContravariantMonoidal[G[_]](implicit arg0: ContravariantMonoidal[G]): ContravariantMonoidal[[α]F[G[α]]]
Compose an
Applicative[F]
and aContravariantMonoidal[G]
into aContravariantMonoidal[λ[α => F[G[α]]]]
.Compose an
Applicative[F]
and aContravariantMonoidal[G]
into aContravariantMonoidal[λ[α => F[G[α]]]]
.Example:
scala> import cats.kernel.Comparison scala> import cats.implicits._ // compares strings by alphabetical order scala> val alpha: Order[String] = Order[String] // compares strings by their length scala> val strLength: Order[String] = Order.by[String, Int](_.length) scala> val stringOrders: List[Order[String]] = List(alpha, strLength) // first comparison is with alpha order, second is with string length scala> stringOrders.map(o => o.comparison("abc", "de")) res0: List[Comparison] = List(LessThan, GreaterThan) scala> val le = Applicative[List].composeContravariantMonoidal[Order] // create Int orders that convert ints to strings and then use the string orders scala> val intOrders: List[Order[Int]] = le.contramap(stringOrders)(_.toString) // first comparison is with alpha order, second is with string length scala> intOrders.map(o => o.comparison(12, 3)) res1: List[Comparison] = List(LessThan, GreaterThan) // create the `product` of the string order list and the int order list // `p` contains a list of the following orders: // 1. (alpha comparison on strings followed by alpha comparison on ints) // 2. (alpha comparison on strings followed by length comparison on ints) // 3. (length comparison on strings followed by alpha comparison on ints) // 4. (length comparison on strings followed by length comparison on ints) scala> val p: List[Order[(String, Int)]] = le.product(stringOrders, intOrders) scala> p.map(o => o.comparison(("abc", 12), ("def", 3))) res2: List[Comparison] = List(LessThan, LessThan, LessThan, GreaterThan)
- Definition Classes
- Applicative
-
def
composeFunctor[G[_]](implicit arg0: Functor[G]): Invariant[[α]F[G[α]]]
Compose Invariant
F[_]
and FunctorG[_]
then produceInvariant[F[G[_]]]
using F'simap
and G'smap
.Compose Invariant
F[_]
and FunctorG[_]
then produceInvariant[F[G[_]]]
using F'simap
and G'smap
.Example:
scala> import cats.implicits._ scala> import scala.concurrent.duration._ scala> val durSemigroupList: Semigroup[List[FiniteDuration]] = | Invariant[Semigroup] | .composeFunctor[List] | .imap(Semigroup[List[Long]])(Duration.fromNanos)(_.toNanos) scala> durSemigroupList.combine(List(2.seconds, 3.seconds), List(4.seconds)) res1: List[FiniteDuration] = List(2 seconds, 3 seconds, 4 seconds)
- Definition Classes
- Invariant
-
def
ensure[A](fa: F[A])(error: ⇒ E)(predicate: (A) ⇒ Boolean): F[A]
Turns a successful value into an error if it does not satisfy a given predicate.
-
def
ensureOr[A](fa: F[A])(error: (A) ⇒ E)(predicate: (A) ⇒ Boolean): F[A]
Turns a successful value into an error specified by the
error
function if it does not satisfy a given predicate. -
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
flatTap[A, B](fa: F[A])(f: (A) ⇒ F[B]): F[A]
Apply a monadic function and discard the result while keeping the effect.
Apply a monadic function and discard the result while keeping the effect.
scala> import cats._, implicits._ scala> Option(1).flatTap(_ => None) res0: Option[Int] = None scala> Option(1).flatTap(_ => Some("123")) res1: Option[Int] = Some(1) scala> def nCats(n: Int) = List.fill(n)("cat") nCats: (n: Int)List[String] scala> List[Int](0).flatTap(nCats) res2: List[Int] = List() scala> List[Int](4).flatTap(nCats) res3: List[Int] = List(4, 4, 4, 4)
- Definition Classes
- FlatMap
-
def
flatten[A](ffa: F[F[A]]): F[A]
"flatten" a nested
F
ofF
structure into a single-layerF
structure."flatten" a nested
F
ofF
structure into a single-layerF
structure.This is also commonly called
join
.Example:
scala> import cats.Eval scala> import cats.implicits._ scala> val nested: Eval[Eval[Int]] = Eval.now(Eval.now(3)) scala> val flattened: Eval[Int] = nested.flatten scala> flattened.value res0: Int = 3
- Definition Classes
- FlatMap
-
final
def
fmap[A, B](fa: F[A])(f: (A) ⇒ B): F[B]
Alias for map, since map can't be injected as syntax if the implementing type already had a built-in
.map
method.Alias for map, since map can't be injected as syntax if the implementing type already had a built-in
.map
method.Example:
scala> import cats.implicits._ scala> val m: Map[Int, String] = Map(1 -> "hi", 2 -> "there", 3 -> "you") scala> m.fmap(_ ++ "!") res0: Map[Int,String] = Map(1 -> hi!, 2 -> there!, 3 -> you!)
- Definition Classes
- Functor
-
def
foreverM[A, B](fa: F[A]): F[B]
Like an infinite loop of >> calls.
Like an infinite loop of >> calls. This is most useful effect loops that you want to run forever in for instance a server.
This will be an infinite loop, or it will return an F[Nothing].
Be careful using this. For instance, a List of length k will produce a list of length k^n at iteration n. This means if k = 0, we return an empty list, if k = 1, we loop forever allocating single element lists, but if we have a k > 1, we will allocate exponentially increasing memory and very quickly OOM.
- Definition Classes
- FlatMap
- Annotations
- @noop()
-
def
fproduct[A, B](fa: F[A])(f: (A) ⇒ B): F[(A, B)]
Tuple the values in fa with the result of applying a function with the value
Tuple the values in fa with the result of applying a function with the value
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> Functor[Option].fproduct(Option(42))(_.toString) res0: Option[(Int, String)] = Some((42,42))
- Definition Classes
- Functor
-
def
fproductLeft[A, B](fa: F[A])(f: (A) ⇒ B): F[(B, A)]
Pair the result of function application with
A
.Pair the result of function application with
A
.Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> Functor[Option].fproductLeft(Option(42))(_.toString) res0: Option[(String, Int)] = Some((42,42))
- Definition Classes
- Functor
-
def
fromEither[A](x: Either[E, A]): F[A]
Convert from scala.Either
Convert from scala.Either
Example:
scala> import cats.ApplicativeError scala> import cats.instances.option._ scala> ApplicativeError[Option, Unit].fromEither(Right(1)) res0: scala.Option[Int] = Some(1) scala> ApplicativeError[Option, Unit].fromEither(Left(())) res1: scala.Option[Nothing] = None
- Definition Classes
- ApplicativeError
-
def
fromOption[A](oa: Option[A], ifEmpty: ⇒ E): F[A]
Convert from scala.Option
Convert from scala.Option
Example:
scala> import cats.implicits._ scala> import cats.ApplicativeError scala> val F = ApplicativeError[Either[String, *], String] scala> F.fromOption(Some(1), "Empty") res0: scala.Either[String, Int] = Right(1) scala> F.fromOption(Option.empty[Int], "Empty") res1: scala.Either[String, Int] = Left(Empty)
- Definition Classes
- ApplicativeError
-
def
fromTry[A](t: Try[A])(implicit ev: <:<[Throwable, E]): F[A]
If the error type is Throwable, we can convert from a scala.util.Try
If the error type is Throwable, we can convert from a scala.util.Try
- Definition Classes
- ApplicativeError
-
def
fromValidated[A](x: Validated[E, A]): F[A]
Convert from cats.data.Validated
Convert from cats.data.Validated
Example:
scala> import cats.implicits._ scala> import cats.ApplicativeError scala> ApplicativeError[Option, Unit].fromValidated(1.valid[Unit]) res0: scala.Option[Int] = Some(1) scala> ApplicativeError[Option, Unit].fromValidated(().invalid[Int]) res1: scala.Option[Int] = None
- Definition Classes
- ApplicativeError
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native() @IntrinsicCandidate()
-
def
handleError[A](fa: F[A])(f: (E) ⇒ A): F[A]
Handle any error, by mapping it to an
A
value.Handle any error, by mapping it to an
A
value.- Definition Classes
- ApplicativeError
- See also
handleErrorWith to map to an
F[A]
value instead of simply anA
value.recover to only recover from certain errors.
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native() @IntrinsicCandidate()
-
def
ifElseM[A](branches: (F[Boolean], F[A])*)(els: F[A]): F[A]
Simulates an if/else-if/else in the context of an F.
Simulates an if/else-if/else in the context of an F. It evaluates conditions until one evaluates to true, and returns the associated F[A]. If no condition is true, returns els.
scala> import cats._ scala> Monad[Eval].ifElseM(Eval.later(false) -> Eval.later(1), Eval.later(true) -> Eval.later(2))(Eval.later(5)).value res0: Int = 2
Based on a gist by Daniel Spiewak with a stack-safe implementation due to P. Oscar Boykin
- Definition Classes
- Monad
- Annotations
- @noop()
- See also
See https://gitter.im/typelevel/cats-effect?at=5f297e4314c413356f56d230 for the discussion.
-
def
ifF[A](fb: F[Boolean])(ifTrue: ⇒ A, ifFalse: ⇒ A): F[A]
Lifts
if
to FunctorLifts
if
to FunctorExample:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForList scala> Functor[List].ifF(List(true, false, false))(1, 0) res0: List[Int] = List(1, 0, 0)
- Definition Classes
- Functor
- Annotations
- @noop()
-
def
ifM[B](fa: F[Boolean])(ifTrue: ⇒ F[B], ifFalse: ⇒ F[B]): F[B]
if
lifted into monad.if
lifted into monad.- Definition Classes
- FlatMap
- Annotations
- @noop()
-
def
imap[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B) ⇒ A): F[B]
Transform an
F[A]
into anF[B]
by providing a transformation fromA
toB
and one fromB
toA
.Transform an
F[A]
into anF[B]
by providing a transformation fromA
toB
and one fromB
toA
.Example:
scala> import cats.implicits._ scala> import scala.concurrent.duration._ scala> val durSemigroup: Semigroup[FiniteDuration] = | Invariant[Semigroup].imap(Semigroup[Long])(Duration.fromNanos)(_.toNanos) scala> durSemigroup.combine(2.seconds, 3.seconds) res1: FiniteDuration = 5 seconds
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
-
def
iterateForeverM[A, B](a: A)(f: (A) ⇒ F[A]): F[B]
iterateForeverM is almost exclusively useful for effect types.
iterateForeverM is almost exclusively useful for effect types. For instance, A may be some state, we may take the current state, run some effect to get a new state and repeat.
- Definition Classes
- FlatMap
- Annotations
- @noop()
-
def
iterateUntil[A](f: F[A])(p: (A) ⇒ Boolean): F[A]
Execute an action repeatedly until its result satisfies the given predicate and return that result, discarding all others.
Execute an action repeatedly until its result satisfies the given predicate and return that result, discarding all others.
- Definition Classes
- Monad
-
def
iterateUntilM[A](init: A)(f: (A) ⇒ F[A])(p: (A) ⇒ Boolean): F[A]
Apply a monadic function iteratively until its result satisfies the given predicate and return that result.
Apply a monadic function iteratively until its result satisfies the given predicate and return that result.
- Definition Classes
- Monad
-
def
iterateWhile[A](f: F[A])(p: (A) ⇒ Boolean): F[A]
Execute an action repeatedly until its result fails to satisfy the given predicate and return that result, discarding all others.
Execute an action repeatedly until its result fails to satisfy the given predicate and return that result, discarding all others.
- Definition Classes
- Monad
-
def
iterateWhileM[A](init: A)(f: (A) ⇒ F[A])(p: (A) ⇒ Boolean): F[A]
Apply a monadic function iteratively until its result fails to satisfy the given predicate and return that result.
Apply a monadic function iteratively until its result fails to satisfy the given predicate and return that result.
- Definition Classes
- Monad
-
def
lift[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[B]
Lift a function f to operate on Functors
Lift a function f to operate on Functors
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> val o = Option(42) scala> Functor[Option].lift((x: Int) => x + 10)(o) res0: Option[Int] = Some(52)
- Definition Classes
- Functor
-
def
map[A, B](fa: F[A])(f: (A) ⇒ B): F[B]
- Definition Classes
- Monad → Applicative → Functor
-
def
map10[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map11[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map12[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map13[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map14[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map15[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map16[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map17[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map18[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map19[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map2[A, B, Z](fa: F[A], fb: F[B])(f: (A, B) ⇒ Z): F[Z]
Applies the pure (binary) function f to the effectful values fa and fb.
Applies the pure (binary) function f to the effectful values fa and fb.
map2 can be seen as a binary version of cats.Functor#map.
Example:
scala> import cats.implicits._ scala> val someInt: Option[Int] = Some(3) scala> val noneInt: Option[Int] = None scala> val someLong: Option[Long] = Some(4L) scala> val noneLong: Option[Long] = None scala> Apply[Option].map2(someInt, someLong)((i, l) => i.toString + l.toString) res0: Option[String] = Some(34) scala> Apply[Option].map2(someInt, noneLong)((i, l) => i.toString + l.toString) res0: Option[String] = None scala> Apply[Option].map2(noneInt, noneLong)((i, l) => i.toString + l.toString) res0: Option[String] = None scala> Apply[Option].map2(noneInt, someLong)((i, l) => i.toString + l.toString) res0: Option[String] = None
-
def
map20[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map21[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map22[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20], f21: F[A21])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map2Eval[A, B, Z](fa: F[A], fb: Eval[F[B]])(f: (A, B) ⇒ Z): Eval[F[Z]]
Similar to map2 but uses Eval to allow for laziness in the
F[B]
argument.Similar to map2 but uses Eval to allow for laziness in the
F[B]
argument. This can allow for "short-circuiting" of computations.NOTE: the default implementation of
map2Eval
does not short-circuit computations. For data structures that can benefit from laziness, Apply instances should override this method.In the following example,
x.map2(bomb)(_ + _)
would result in an error, butmap2Eval
"short-circuits" the computation.x
isNone
and thus the result ofbomb
doesn't even need to be evaluated in order to determine that the result ofmap2Eval
should beNone
.scala> import cats.{Eval, Later} scala> import cats.implicits._ scala> val bomb: Eval[Option[Int]] = Later(sys.error("boom")) scala> val x: Option[Int] = None scala> x.map2Eval(bomb)(_ + _).value res0: Option[Int] = None
-
def
map3[A0, A1, A2, Z](f0: F[A0], f1: F[A1], f2: F[A2])(f: (A0, A1, A2) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map4[A0, A1, A2, A3, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3])(f: (A0, A1, A2, A3) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map5[A0, A1, A2, A3, A4, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4])(f: (A0, A1, A2, A3, A4) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map6[A0, A1, A2, A3, A4, A5, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5])(f: (A0, A1, A2, A3, A4, A5) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map7[A0, A1, A2, A3, A4, A5, A6, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6])(f: (A0, A1, A2, A3, A4, A5, A6) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map8[A0, A1, A2, A3, A4, A5, A6, A7, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7])(f: (A0, A1, A2, A3, A4, A5, A6, A7) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
map9[A0, A1, A2, A3, A4, A5, A6, A7, A8, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8])(f: (A0, A1, A2, A3, A4, A5, A6, A7, A8) ⇒ Z): F[Z]
- Definition Classes
- ApplyArityFunctions
-
def
mproduct[A, B](fa: F[A])(f: (A) ⇒ F[B]): F[(A, B)]
Pair
A
with the result of function application.Pair
A
with the result of function application.Example:
scala> import cats.implicits._ scala> List("12", "34", "56").mproduct(_.toList) res0: List[(String, Char)] = List((12,1), (12,2), (34,3), (34,4), (56,5), (56,6))
- Definition Classes
- FlatMap
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @IntrinsicCandidate()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @IntrinsicCandidate()
-
def
onError[A](fa: F[A])(pf: PartialFunction[E, F[Unit]]): F[A]
Execute a callback on certain errors, then rethrow them.
Execute a callback on certain errors, then rethrow them. Any non matching error is rethrown as well.
In the following example, only one of the errors is logged, but they are both rethrown, to be possibly handled by another layer of the program:
scala> import cats._, data._, implicits._ scala> case class Err(msg: String) scala> type F[A] = EitherT[State[String, *], Err, A] scala> val action: PartialFunction[Err, F[Unit]] = { | case Err("one") => EitherT.liftF(State.set("one")) | } scala> val prog1: F[Int] = (Err("one")).raiseError[F, Int] scala> val prog2: F[Int] = (Err("two")).raiseError[F, Int] scala> prog1.onError(action).value.run("").value res0: (String, Either[Err,Int]) = (one,Left(Err(one))) scala> prog2.onError(action).value.run("").value res1: (String, Either[Err,Int]) = ("",Left(Err(two)))
- Definition Classes
- ApplicativeError
-
def
point[A](a: A): F[A]
point
lifts any value into a Monoidal Functor.point
lifts any value into a Monoidal Functor.Example:
scala> import cats.implicits._ scala> InvariantMonoidal[Option].point(10) res0: Option[Int] = Some(10)
- Definition Classes
- InvariantMonoidal
-
def
product[A, B](fa: F[A], fb: F[B]): F[(A, B)]
Combine an
F[A]
and anF[B]
into anF[(A, B)]
that maintains the effects of bothfa
andfb
.Combine an
F[A]
and anF[B]
into anF[(A, B)]
that maintains the effects of bothfa
andfb
.Example:
scala> import cats.implicits._ scala> val noneInt: Option[Int] = None scala> val some3: Option[Int] = Some(3) scala> val noneString: Option[String] = None scala> val someFoo: Option[String] = Some("foo") scala> Semigroupal[Option].product(noneInt, noneString) res0: Option[(Int, String)] = None scala> Semigroupal[Option].product(noneInt, someFoo) res1: Option[(Int, String)] = None scala> Semigroupal[Option].product(some3, noneString) res2: Option[(Int, String)] = None scala> Semigroupal[Option].product(some3, someFoo) res3: Option[(Int, String)] = Some((3,foo))
- Definition Classes
- FlatMap → Apply → Semigroupal
-
def
productL[A, B](fa: F[A])(fb: F[B]): F[A]
Compose two actions, discarding any value produced by the second.
Compose two actions, discarding any value produced by the second.
- Definition Classes
- FlatMap → Apply
- See also
productR to discard the value of the first instead. Example:
scala> import cats.implicits._ scala> import cats.data.Validated scala> import Validated.{Valid, Invalid} scala> type ErrOr[A] = Validated[String, A] scala> val validInt: ErrOr[Int] = Valid(3) scala> val validBool: ErrOr[Boolean] = Valid(true) scala> val invalidInt: ErrOr[Int] = Invalid("Invalid int.") scala> val invalidBool: ErrOr[Boolean] = Invalid("Invalid boolean.") scala> Apply[ErrOr].productL(validInt)(validBool) res0: ErrOr[Int] = Valid(3) scala> Apply[ErrOr].productL(invalidInt)(validBool) res1: ErrOr[Int] = Invalid(Invalid int.) scala> Apply[ErrOr].productL(validInt)(invalidBool) res2: ErrOr[Int] = Invalid(Invalid boolean.) scala> Apply[ErrOr].productL(invalidInt)(invalidBool) res3: ErrOr[Int] = Invalid(Invalid int.Invalid boolean.)
-
def
productLEval[A, B](fa: F[A])(fb: Eval[F[B]]): F[A]
Sequentially compose two actions, discarding any value produced by the second.
Sequentially compose two actions, discarding any value produced by the second. This variant of productL also lets you define the evaluation strategy of the second action. For instance you can evaluate it only after the first action has finished:
scala> import cats.Eval scala> import cats.implicits._ scala> var count = 0 scala> val fa: Option[Int] = Some(3) scala> def fb: Option[Unit] = Some(count += 1) scala> fa.productLEval(Eval.later(fb)) res0: Option[Int] = Some(3) scala> assert(count == 1) scala> none[Int].productLEval(Eval.later(fb)) res1: Option[Int] = None scala> assert(count == 1)
- Definition Classes
- FlatMap
-
def
productR[A, B](fa: F[A])(fb: F[B]): F[B]
Compose two actions, discarding any value produced by the first.
Compose two actions, discarding any value produced by the first.
- Definition Classes
- FlatMap → Apply
- See also
productL to discard the value of the second instead. Example:
scala> import cats.implicits._ scala> import cats.data.Validated scala> import Validated.{Valid, Invalid} scala> type ErrOr[A] = Validated[String, A] scala> val validInt: ErrOr[Int] = Valid(3) scala> val validBool: ErrOr[Boolean] = Valid(true) scala> val invalidInt: ErrOr[Int] = Invalid("Invalid int.") scala> val invalidBool: ErrOr[Boolean] = Invalid("Invalid boolean.") scala> Apply[ErrOr].productR(validInt)(validBool) res0: ErrOr[Boolean] = Valid(true) scala> Apply[ErrOr].productR(invalidInt)(validBool) res1: ErrOr[Boolean] = Invalid(Invalid int.) scala> Apply[ErrOr].productR(validInt)(invalidBool) res2: ErrOr[Boolean] = Invalid(Invalid boolean.) scala> Apply[ErrOr].productR(invalidInt)(invalidBool) res3: ErrOr[Boolean] = Invalid(Invalid int.Invalid boolean.)
-
def
productREval[A, B](fa: F[A])(fb: Eval[F[B]]): F[B]
Sequentially compose two actions, discarding any value produced by the first.
Sequentially compose two actions, discarding any value produced by the first. This variant of productR also lets you define the evaluation strategy of the second action. For instance you can evaluate it only after the first action has finished:
scala> import cats.Eval scala> import cats.implicits._ scala> val fa: Option[Int] = Some(3) scala> def fb: Option[String] = Some("foo") scala> fa.productREval(Eval.later(fb)) res0: Option[String] = Some(foo)
- Definition Classes
- FlatMap
-
def
raiseUnless(cond: Boolean)(e: ⇒ E): F[Unit]
Returns
raiseError
whencond
is false, otherwiseF.unit
Returns
raiseError
whencond
is false, otherwiseF.unit
- Definition Classes
- ApplicativeError
val tooMany = 5 val x: Int = ??? F.raiseUnless(x < tooMany)(new IllegalArgumentException("Too many"))
Example: -
def
raiseWhen(cond: Boolean)(e: ⇒ E): F[Unit]
Returns
raiseError
when thecond
is true, otherwiseF.unit
Returns
raiseError
when thecond
is true, otherwiseF.unit
- Definition Classes
- ApplicativeError
val tooMany = 5 val x: Int = ??? F.raiseWhen(x >= tooMany)(new IllegalArgumentException("Too many"))
Example: -
def
recover[A](fa: F[A])(pf: PartialFunction[E, A]): F[A]
Recover from certain errors by mapping them to an
A
value.Recover from certain errors by mapping them to an
A
value.- Definition Classes
- ApplicativeError
- See also
handleError to handle any/all errors.
recoverWith to recover from certain errors by mapping them to
F[A]
values.
-
def
recoverWith[A](fa: F[A])(pf: PartialFunction[E, F[A]]): F[A]
Recover from certain errors by mapping them to an
F[A]
value.Recover from certain errors by mapping them to an
F[A]
value.- Definition Classes
- ApplicativeError
- See also
handleErrorWith to handle any/all errors.
recover to recover from certain errors by mapping them to
A
values.
-
def
redeem[A, B](fa: F[A])(recover: (E) ⇒ B, f: (A) ⇒ B): F[B]
Returns a new value that transforms the result of the source, given the
recover
ormap
functions, which get executed depending on whether the result is successful or if it ends in error.Returns a new value that transforms the result of the source, given the
recover
ormap
functions, which get executed depending on whether the result is successful or if it ends in error.This is an optimization on usage of attempt and map, this equivalence being available:
fa.redeem(fe, fs) <-> fa.attempt.map(_.fold(fe, fs))
Usage of
redeem
subsumes handleError because:fa.redeem(fe, id) <-> fa.handleError(fe)
Implementations are free to override it in order to optimize error recovery.
- fa
is the source whose result is going to get transformed
- recover
is the function that gets called to recover the source in case of error
- Definition Classes
- ApplicativeError
- See also
-
def
redeemWith[A, B](fa: F[A])(recover: (E) ⇒ F[B], bind: (A) ⇒ F[B]): F[B]
Returns a new value that transforms the result of the source, given the
recover
orbind
functions, which get executed depending on whether the result is successful or if it ends in error.Returns a new value that transforms the result of the source, given the
recover
orbind
functions, which get executed depending on whether the result is successful or if it ends in error.This is an optimization on usage of attempt and flatMap, this equivalence being available:
fa.redeemWith(fe, fs) <-> fa.attempt.flatMap(_.fold(fe, fs))
Usage of
redeemWith
subsumes handleErrorWith because:fa.redeemWith(fe, F.pure) <-> fa.handleErrorWith(fe)
Usage of
redeemWith
also subsumes flatMap because:fa.redeemWith(F.raiseError, fs) <-> fa.flatMap(fs)
Implementations are free to override it in order to optimize error recovery.
- fa
is the source whose result is going to get transformed
- recover
is the function that gets called to recover the source in case of error
- bind
is the function that gets to transform the source in case of success
- See also
redeem, attempt and handleErrorWith
-
def
replicateA[A](n: Int, fa: F[A]): F[List[A]]
Given
fa
andn
, applyfa
n
times to construct anF[List[A]]
value.Given
fa
andn
, applyfa
n
times to construct anF[List[A]]
value.Example:
scala> import cats.data.State scala> type Counter[A] = State[Int, A] scala> val getAndIncrement: Counter[Int] = State { i => (i + 1, i) } scala> val getAndIncrement5: Counter[List[Int]] = | Applicative[Counter].replicateA(5, getAndIncrement) scala> getAndIncrement5.run(0).value res0: (Int, List[Int]) = (5,List(0, 1, 2, 3, 4))
- Definition Classes
- Applicative
-
def
rethrow[A, EE <: E](fa: F[Either[EE, A]]): F[A]
Inverse of
attempt
Inverse of
attempt
Example:
scala> import cats.implicits._ scala> import scala.util.{Try, Success} scala> val a: Try[Either[Throwable, Int]] = Success(Left(new java.lang.Exception)) scala> a.rethrow res0: scala.util.Try[Int] = Failure(java.lang.Exception) scala> val b: Try[Either[Throwable, Int]] = Success(Right(1)) scala> b.rethrow res1: scala.util.Try[Int] = Success(1)
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): String
- Definition Classes
- AnyRef → Any
-
def
tuple10[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple11[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple12[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple13[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple14[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple15[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple16[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple17[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple18[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple19[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple2[A, B](f1: F[A], f2: F[B]): F[(A, B)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple20[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple21[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple22[A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8], f9: F[A9], f10: F[A10], f11: F[A11], f12: F[A12], f13: F[A13], f14: F[A14], f15: F[A15], f16: F[A16], f17: F[A17], f18: F[A18], f19: F[A19], f20: F[A20], f21: F[A21]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple3[A0, A1, A2, Z](f0: F[A0], f1: F[A1], f2: F[A2]): F[(A0, A1, A2)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple4[A0, A1, A2, A3, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3]): F[(A0, A1, A2, A3)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple5[A0, A1, A2, A3, A4, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4]): F[(A0, A1, A2, A3, A4)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple6[A0, A1, A2, A3, A4, A5, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5]): F[(A0, A1, A2, A3, A4, A5)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple7[A0, A1, A2, A3, A4, A5, A6, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6]): F[(A0, A1, A2, A3, A4, A5, A6)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple8[A0, A1, A2, A3, A4, A5, A6, A7, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7]): F[(A0, A1, A2, A3, A4, A5, A6, A7)]
- Definition Classes
- ApplyArityFunctions
-
def
tuple9[A0, A1, A2, A3, A4, A5, A6, A7, A8, Z](f0: F[A0], f1: F[A1], f2: F[A2], f3: F[A3], f4: F[A4], f5: F[A5], f6: F[A6], f7: F[A7], f8: F[A8]): F[(A0, A1, A2, A3, A4, A5, A6, A7, A8)]
- Definition Classes
- ApplyArityFunctions
-
def
tupleLeft[A, B](fa: F[A], b: B): F[(B, A)]
Tuples the
A
value inF[A]
with the suppliedB
value, with theB
value on the left.Tuples the
A
value inF[A]
with the suppliedB
value, with theB
value on the left.Example:
scala> import scala.collection.immutable.Queue scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForQueue scala> Functor[Queue].tupleLeft(Queue("hello", "world"), 42) res0: scala.collection.immutable.Queue[(Int, String)] = Queue((42,hello), (42,world))
- Definition Classes
- Functor
-
def
tupleRight[A, B](fa: F[A], b: B): F[(A, B)]
Tuples the
A
value inF[A]
with the suppliedB
value, with theB
value on the right.Tuples the
A
value inF[A]
with the suppliedB
value, with theB
value on the right.Example:
scala> import scala.collection.immutable.Queue scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForQueue scala> Functor[Queue].tupleRight(Queue("hello", "world"), 42) res0: scala.collection.immutable.Queue[(String, Int)] = Queue((hello,42), (world,42))
- Definition Classes
- Functor
-
def
unit: F[Unit]
Returns an
F[Unit]
value, equivalent withpure(())
.Returns an
F[Unit]
value, equivalent withpure(())
.A useful shorthand, also allowing implementations to optimize the returned reference (e.g. it can be a
val
).Example:
scala> import cats.implicits._ scala> Applicative[Option].unit res0: Option[Unit] = Some(())
- Definition Classes
- Applicative → InvariantMonoidal
-
def
unlessA[A](cond: Boolean)(f: ⇒ F[A]): F[Unit]
Returns the given argument (mapped to Unit) if
cond
isfalse
, otherwise, unit lifted into F.Returns the given argument (mapped to Unit) if
cond
isfalse
, otherwise, unit lifted into F.Example:
scala> import cats.implicits._ scala> Applicative[List].unlessA(true)(List(1, 2, 3)) res0: List[Unit] = List(()) scala> Applicative[List].unlessA(false)(List(1, 2, 3)) res1: List[Unit] = List((), (), ()) scala> Applicative[List].unlessA(true)(List.empty[Int]) res2: List[Unit] = List(()) scala> Applicative[List].unlessA(false)(List.empty[Int]) res3: List[Unit] = List()
- Definition Classes
- Applicative
-
def
untilDefinedM[A](foa: F[Option[A]]): F[A]
This repeats an F until we get defined values.
This repeats an F until we get defined values. This can be useful for polling type operations on State (or RNG) Monads, or in effect monads.
- Definition Classes
- FlatMap
- Annotations
- @noop()
-
def
untilM[G[_], A](f: F[A])(cond: ⇒ F[Boolean])(implicit G: Alternative[G]): F[G[A]]
Execute an action repeatedly until the
Boolean
condition returnstrue
.Execute an action repeatedly until the
Boolean
condition returnstrue
. The condition is evaluated after the loop body. Collects results into an arbitraryAlternative
value, such as aVector
. This implementation uses append on each evaluation result, so avoid data structures with non-constant append performance, e.g.List
.- Definition Classes
- Monad
-
def
untilM_[A](f: F[A])(cond: ⇒ F[Boolean]): F[Unit]
Execute an action repeatedly until the
Boolean
condition returnstrue
.Execute an action repeatedly until the
Boolean
condition returnstrue
. The condition is evaluated after the loop body. Discards results.- Definition Classes
- Monad
-
def
unzip[A, B](fab: F[(A, B)]): (F[A], F[B])
Un-zips an
F[(A, B)]
consisting of element pairs or Tuple2 into two separate F's tupled.Un-zips an
F[(A, B)]
consisting of element pairs or Tuple2 into two separate F's tupled.NOTE: Check for effect duplication, possibly memoize before
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForList scala> Functor[List].unzip(List((1,2), (3, 4))) res0: (List[Int], List[Int]) = (List(1, 3),List(2, 4))
- Definition Classes
- Functor
- Annotations
- @noop()
-
def
void[A](fa: F[A]): F[Unit]
Empty the fa of the values, preserving the structure
Empty the fa of the values, preserving the structure
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForList scala> Functor[List].void(List(1,2,3)) res0: List[Unit] = List((), (), ())
- Definition Classes
- Functor
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... ) @native()
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
def
whenA[A](cond: Boolean)(f: ⇒ F[A]): F[Unit]
Returns the given argument (mapped to Unit) if
cond
istrue
, otherwise, unit lifted into F.Returns the given argument (mapped to Unit) if
cond
istrue
, otherwise, unit lifted into F.Example:
scala> import cats.implicits._ scala> Applicative[List].whenA(true)(List(1, 2, 3)) res0: List[Unit] = List((), (), ()) scala> Applicative[List].whenA(false)(List(1, 2, 3)) res1: List[Unit] = List(()) scala> Applicative[List].whenA(true)(List.empty[Int]) res2: List[Unit] = List() scala> Applicative[List].whenA(false)(List.empty[Int]) res3: List[Unit] = List(())
- Definition Classes
- Applicative
-
def
whileM[G[_], A](p: F[Boolean])(body: ⇒ F[A])(implicit G: Alternative[G]): F[G[A]]
Execute an action repeatedly as long as the given
Boolean
expression returnstrue
.Execute an action repeatedly as long as the given
Boolean
expression returnstrue
. The condition is evaluated before the loop body. Collects the results into an arbitraryAlternative
value, such as aVector
. This implementation uses append on each evaluation result, so avoid data structures with non-constant append performance, e.g.List
.- Definition Classes
- Monad
- Annotations
- @noop()
-
def
whileM_[A](p: F[Boolean])(body: ⇒ F[A]): F[Unit]
Execute an action repeatedly as long as the given
Boolean
expression returnstrue
.Execute an action repeatedly as long as the given
Boolean
expression returnstrue
. The condition is evaluated before the loop body. Discards results.- Definition Classes
- Monad
- Annotations
- @noop()
-
def
widen[A, B >: A](fa: F[A]): F[B]
Lifts natural subtyping covariance of covariant Functors.
Lifts natural subtyping covariance of covariant Functors.
NOTE: In certain (perhaps contrived) situations that rely on universal equality this can result in a
ClassCastException
, because it is implemented as a type cast. It could be implemented asmap(identity)
, but according to the functor laws, that should be equal tofa
, and a type cast is often much more performant. See this example ofwiden
creating aClassCastException
.Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> val s = Some(42) scala> Functor[Option].widen(s) res0: Option[Int] = Some(42)
- Definition Classes
- Functor
Deprecated Value Members
-
def
finalize(): Unit
- Attributes
- protected[lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] ) @Deprecated
- Deprecated
-
def
ifA[A](fcond: F[Boolean])(ifTrue: F[A], ifFalse: F[A]): F[A]
- Definition Classes
- Apply
- Annotations
- @noop() @deprecated
- Deprecated
(Since version 2.6.2) Dangerous method, use ifM (a flatMap) or ifF (a map) instead
Inherited from Monad[F]
Inherited from FlatMap[F]
Inherited from ApplicativeError[F, E]
Inherited from Applicative[F]
Inherited from InvariantMonoidal[F]
Inherited from Apply[F]
Inherited from ApplyArityFunctions[F]
Inherited from InvariantSemigroupal[F]
Inherited from Semigroupal[F]
Inherited from Functor[F]
Inherited from Invariant[F]
Inherited from Serializable
Inherited from Serializable
Inherited from AnyRef
Inherited from Any
Ungrouped
ap arity
Higher-arity ap methods
map arity
Higher-arity map methods
tuple arity
Higher-arity tuple methods