BIOCatsSpawnImpl
Attributes
- Graph
- Supertypes
- trait BIOCatsSpawn[F]trait GenSpawn[[_] =>> F[Throwable, _$93], Throwable]trait Unique[[_] =>> F[Throwable, _$93]]class BIOCatsMonadCancel[F]trait MonadCancel[[_] =>> F[Throwable, _$93], Throwable]trait MonadError[[_] =>> F[Throwable, _$93], Throwable]trait ApplicativeError[[_] =>> F[Throwable, _$93], Throwable]trait Monad[[_] =>> F[Throwable, _$93]]trait Applicative[[_] =>> F[Throwable, _$93]]trait InvariantMonoidal[[_] =>> F[Throwable, _$93]]trait FlatMap[[_] =>> F[Throwable, _$93]]trait FlatMapArityFunctions[[_] =>> F[Throwable, _$93]]trait Apply[[_] =>> F[Throwable, _$93]]trait ApplyArityFunctions[[_] =>> F[Throwable, _$93]]trait InvariantSemigroupal[[_] =>> F[Throwable, _$93]]trait Semigroupal[[_] =>> F[Throwable, _$93]]trait Functor[[_] =>> F[Throwable, _$93]]trait Invariant[[_] =>> F[Throwable, _$93]]trait Serializableclass Objecttrait Matchableclass Any
Members list
Value members
Concrete methods
Attributes
- Definition Classes
- Unique
Inherited methods
Alias for productR.
Alias for productR.
Attributes
- Inherited from:
- Apply
Alias for productL.
Alias for productL.
Attributes
- Inherited from:
- Apply
Alias for ap.
Alias for ap.
Attributes
- Inherited from:
- Apply
Transform certain errors using pf
and rethrow them.
Non matching errors and successful values are not affected by this function.
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
as adaptErr
- it cannot have the same
name because this would result in ambiguous implicits due to adaptError
having originally been included in the MonadError
API and syntax.
Attributes
- Definition Classes
- MonadError -> ApplicativeError
- Inherited from:
- MonadError
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
Attributes
- Definition Classes
- BIOCatsApplicative -> Apply
- Inherited from:
- BIOCatsApplicative
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
ap2 is a binary version of ap, defined in terms of ap.
ap2 is a binary version of ap, defined in terms of ap.
Attributes
- Definition Classes
- FlatMap -> Apply
- Inherited from:
- FlatMap
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- GenSpawn
Replaces the A
value in F[A]
with the supplied value.
Replaces the A
value in F[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)
Attributes
- Definition Classes
- BIOCatsFunctor -> Functor
- Inherited from:
- BIOCatsFunctor
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.
Attributes
- Definition Classes
- BIOCatsMonadError -> ApplicativeError
- Inherited from:
- BIOCatsMonadError
Similar to attempt, but it only handles errors of type EE
.
Similar to attempt, but it only handles errors of type EE
.
Attributes
- Inherited from:
- ApplicativeError
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.
Attributes
- Inherited from:
- ApplicativeError
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)
Attributes
- Inherited from:
- MonadError
Returns a Resource that manages the concurrent execution of a fiber. The inner effect can be used to wait on the outcome of the child fiber; it is effectively a join.
Returns a Resource that manages the concurrent execution of a fiber. The inner effect can be used to wait on the outcome of the child fiber; it is effectively a join.
The child fiber is canceled in two cases: either the resource goes out of scope or the parent fiber is canceled. If the child fiber terminates before one of these cases occurs, then cancelation is a no-op. This avoids fiber leaks because the child fiber is always canceled before the parent fiber drops the reference to it.
// Starts a fiber that continously prints "A".
// After 10 seconds, the resource scope exits so the fiber is canceled.
F.background(F.delay(println("A")).foreverM).use { _ =>
F.sleep(10.seconds)
}
Attributes
- fa
the effect for the spawned fiber
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Races the evaluation of two fibers and returns the result of both.
Races the evaluation of two fibers and returns the result of both.
The following rules describe the semantics of both:
- If the winner completes with Outcome.Succeeded, the race waits for the loser to complete. 2. If the winner completes with Outcome.Errored, the race raises the error. The loser is canceled. 3. If the winner completes with Outcome.Canceled, the loser and the race are canceled as well. 4. If the loser completes with Outcome.Succeeded, the race returns the successful value of both fibers. 5. If the loser completes with Outcome.Errored, the race returns the error. 6. If the loser completes with Outcome.Canceled, the race is canceled. 7. If the race is canceled before one or both participants complete, then whichever ones are incomplete are canceled. 8. If the race is masked and is canceled because one or both participants canceled, the fiber will block indefinitely.
Attributes
- fa
the effect for the first racing fiber
- fb
the effect for the second racing fiber
- See also:
bothOutcome for a variant that returns the Outcome of both fibers.
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Races the evaluation of two fibers and returns the Outcome of both. If the race is canceled before one or both participants complete, then then whichever ones are incomplete are canceled.
Races the evaluation of two fibers and returns the Outcome of both. If the race is canceled before one or both participants complete, then then whichever ones are incomplete are canceled.
Attributes
- fa
the effect for the first racing fiber
- fb
the effect for the second racing fiber
- See also:
both for a simpler variant that returns the results of both fibers.
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
A pattern for safely interacting with effectful lifecycles.
A pattern for safely interacting with effectful lifecycles.
If acquire
completes successfully, use
is called. If use
succeeds, fails, or is
canceled, release
is guaranteed to be called exactly once.
acquire
is uncancelable. release
is uncancelable. use
is cancelable by default, but
can be masked.
Attributes
- acquire
the lifecycle acquisition action
- release
the lifecycle release action
- use
the effect to which the lifecycle is scoped, whose result is the return value of this function
- See also:
bracketCase for a more powerful variant
Resource for a composable datatype encoding of effectful lifecycles
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
A pattern for safely interacting with effectful lifecycles.
A pattern for safely interacting with effectful lifecycles.
If acquire
completes successfully, use
is called. If use
succeeds, fails, or is
canceled, release
is guaranteed to be called exactly once.
acquire
is uncancelable. release
is uncancelable. use
is cancelable by default, but
can be masked.
Attributes
- acquire
the lifecycle acquisition action
- release
the lifecycle release action which depends on the outcome of
use
- use
the effect to which the lifecycle is scoped, whose result is the return value of this function
- See also:
bracketFull for a more powerful variant
Resource for a composable datatype encoding of effectful lifecycles
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
A pattern for safely interacting with effectful lifecycles.
A pattern for safely interacting with effectful lifecycles.
If acquire
completes successfully, use
is called. If use
succeeds, fails, or is
canceled, release
is guaranteed to be called exactly once.
If use
succeeds the returned value B
is returned. If use
returns an exception, the
exception is returned.
acquire
is uncancelable by default, but can be unmasked. release
is uncancelable. use
is cancelable by default, but can be masked.
Attributes
- acquire
the lifecycle acquisition action which can be canceled
- release
the lifecycle release action which depends on the outcome of
use
- use
the effect to which the lifecycle is scoped, whose result is the return value of this function
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
An effect that requests self-cancelation on the current fiber.
An effect that requests self-cancelation on the current fiber.
canceled
has a return type of F[Unit]
instead of F[Nothing]
due to execution
continuing in a masked region. In the following example, the fiber requests
self-cancelation in a masked region, so cancelation is suppressed until the fiber is
completely unmasked. fa
will run but fb
will not. If canceled
had a return type of
F[Nothing]
, then it would not be possible to continue execution to fa
(there would be
no Nothing
value to pass to the flatMap
).
F.uncancelable { _ =>
F.canceled *> fa
} *> fb
Attributes
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Often E is Throwable. Here we try to call pure or catch and raise.
Often E is Throwable. Here we try to call pure or catch and raise.
Attributes
- Inherited from:
- ApplicativeError
Often E is Throwable. Here we try to call pure or catch and raise
Often E is Throwable. Here we try to call pure or catch and raise
Attributes
- Inherited from:
- ApplicativeError
Evaluates the specified block, catching exceptions of the specified type. Uncaught exceptions are propagated.
Evaluates the specified block, catching exceptions of the specified type. Uncaught exceptions are propagated.
Attributes
- Inherited from:
- ApplicativeError
Introduces a fairness boundary that yields control back to the scheduler of the runtime system. This allows the carrier thread to resume execution of another waiting fiber.
Introduces a fairness boundary that yields control back to the scheduler of the runtime system. This allows the carrier thread to resume execution of another waiting fiber.
This function is primarily useful when performing long-running computation that is outside of the monadic context. For example:
fa.map(data => expensiveWork(data))
In the above, we're assuming that expensiveWork
is a function which is entirely
compute-bound but very long-running. A good rule of thumb is to consider a function
"expensive" when its runtime is around three or more orders of magnitude higher than the
overhead of the map
function itself (which runs in around 5 nanoseconds on modern
hardware). Thus, any expensiveWork
function which requires around 10 microseconds or
longer to execute should be considered "long-running".
The danger is that these types of long-running actions outside of the monadic context can
result in degraded fairness properties. The solution is to add an explicit cede
both
before and after the expensive operation:
(fa <* F.cede).map(data => expensiveWork(data)).guarantee(F.cede)
Note that extremely long-running expensiveWork
functions can still cause fairness issues,
even when used with cede
. This problem is somewhat fundamental to the nature of
scheduling such computation on carrier threads. Whenever possible, it is best to break
apart any such functions into multiple pieces invoked independently (e.g. via chained map
calls) whenever the execution time exceeds five or six orders of magnitude beyond the
overhead of map
itself (around 1 millisecond on most hardware).
Note that cede
is merely a hint to the runtime system; implementations have the liberty
to interpret this method to their liking as long as it obeys the respective laws. For
example, a lawful, but atypical, implementation of this function is F.unit
, in which case
the fairness boundary is a no-op.
Attributes
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Compose an Applicative[F]
and an Applicative[G]
into an
Applicative[λ[α => F[G[α]]]]
.
Compose an Applicative[F]
and an Applicative[G]
into an
Applicative[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)
Attributes
- Inherited from:
- Applicative
Compose Invariant F[_]
and G[_]
then produce Invariant[F[G[_]]]
using their imap
.
Compose Invariant F[_]
and G[_]
then produce Invariant[F[G[_]]]
using their imap
.
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)
Attributes
- Inherited from:
- Invariant
Compose an Apply[F]
and an Apply[G]
into an Apply[λ[α => F[G[α]]]]
.
Compose an Apply[F]
and an Apply[G]
into an Apply[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)
Attributes
- Inherited from:
- Apply
Attributes
- Inherited from:
- Functor
Attributes
- Inherited from:
- InvariantSemigroupal
Compose Invariant F[_]
and Contravariant G[_]
then produce Invariant[F[G[_]]]
using F's imap
and G's contramap
.
Compose Invariant F[_]
and Contravariant G[_]
then produce Invariant[F[G[_]]]
using F's imap
and G's contramap
.
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
Attributes
- Definition Classes
- Functor -> Invariant
- Inherited from:
- Functor
Compose an Applicative[F]
and a ContravariantMonoidal[G]
into a
ContravariantMonoidal[λ[α => F[G[α]]]]
.
Compose an Applicative[F]
and a ContravariantMonoidal[G]
into a
ContravariantMonoidal[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)
Attributes
- Inherited from:
- Applicative
Compose Invariant F[_]
and Functor G[_]
then produce Invariant[F[G[_]]]
using F's imap
and G's map
.
Compose Invariant F[_]
and Functor G[_]
then produce Invariant[F[G[_]]]
using F's imap
and G's map
.
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)
Attributes
- Inherited from:
- Invariant
Turns a successful value into an error if it does not satisfy a given predicate.
Turns a successful value into an error if it does not satisfy a given predicate.
Attributes
- Inherited from:
- MonadError
Turns a successful value into an error specified by the error
function if it does not satisfy a given predicate.
Turns a successful value into an error specified by the error
function if it does not satisfy a given predicate.
Attributes
- Inherited from:
- MonadError
Attributes
- Definition Classes
- BIOCatsMonad -> FlatMap
- Inherited from:
- BIOCatsMonad
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
Attributes
- Inherited from:
- FlatMapArityFunctions
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)
Attributes
- Inherited from:
- FlatMap
"flatten" a nested F
of F
structure into a single-layer F
structure.
"flatten" a nested F
of F
structure into a single-layer F
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
Attributes
- Definition Classes
- BIOCatsMonad -> FlatMap
- Inherited from:
- BIOCatsMonad
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!)
Attributes
- Inherited from:
- Functor
Analogous to productR, but suppresses short-circuiting behavior except for cancelation.
Analogous to productR, but suppresses short-circuiting behavior except for cancelation.
Attributes
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Like an infinite loop of >> calls. This is most useful effect loops that you want to run forever in for instance a server.
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.
Attributes
- Inherited from:
- FlatMap
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))
Attributes
- Inherited from:
- Functor
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))
Attributes
- Inherited from:
- Functor
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
Attributes
- Definition Classes
- BIOCatsMonadError -> ApplicativeError
- Inherited from:
- BIOCatsMonadError
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)
Attributes
- Inherited from:
- ApplicativeError
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
Attributes
- Inherited from:
- ApplicativeError
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
Attributes
- Inherited from:
- ApplicativeError
Specifies an effect that is always invoked after evaluation of fa
completes, regardless
of the outcome.
Specifies an effect that is always invoked after evaluation of fa
completes, regardless
of the outcome.
This function can be thought of as a combination of flatTap, onError, and onCancel.
Attributes
- fa
The effect that is run after
fin
is registered.- fin
The effect to run in the event of a cancelation or error.
- See also:
guaranteeCase for a more powerful variant
Outcome for the various outcomes of evaluation
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Specifies an effect that is always invoked after evaluation of fa
completes, but depends
on the outcome.
Specifies an effect that is always invoked after evaluation of fa
completes, but depends
on the outcome.
This function can be thought of as a combination of flatTap, onError, and onCancel.
Attributes
- fa
The effect that is run after
fin
is registered.- fin
A function that returns the effect to run based on the outcome.
- See also:
bracketCase for a more powerful variant
Outcome for the various outcomes of evaluation
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Handle any error, by mapping it to an A
value.
Handle any error, by mapping it to an A
value.
Attributes
- See also:
handleErrorWith to map to an
F[A]
value instead of simply anA
value.recover to only recover from certain errors.
- Inherited from:
- ApplicativeError
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.
Attributes
- 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.
- Definition Classes
- BIOCatsMonadError -> ApplicativeError
- Inherited from:
- BIOCatsMonadError
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.
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
Attributes
- See also:
See https://gitter.im/typelevel/cats-effect?at=5f297e4314c413356f56d230 for the discussion.
- Inherited from:
- Monad
Lifts if
to Functor
Lifts if
to Functor
Example:
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)
Attributes
- Inherited from:
- Functor
if
lifted into monad.
if
lifted into monad.
Attributes
- Inherited from:
- FlatMap
Transform an F[A]
into an F[B]
by providing a transformation from A
to B
and one from B
to A
.
Transform an F[A]
into an F[B]
by providing a transformation from A
to B
and one from B
to A
.
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
Attributes
- Definition Classes
- Functor -> Invariant
- Inherited from:
- Functor
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.
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.
Attributes
- Inherited from:
- FlatMap
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.
Attributes
- Definition Classes
- BIOCatsMonad -> Monad
- Inherited from:
- BIOCatsMonad
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.
Attributes
- Definition Classes
- BIOCatsMonad -> Monad
- Inherited from:
- BIOCatsMonad
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.
Attributes
- Definition Classes
- BIOCatsMonad -> Monad
- Inherited from:
- BIOCatsMonad
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.
Attributes
- Definition Classes
- BIOCatsMonad -> Monad
- Inherited from:
- BIOCatsMonad
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)
Attributes
- Inherited from:
- Functor
Attributes
- Definition Classes
- BIOCatsFunctor -> Functor
- Inherited from:
- BIOCatsFunctor
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
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
Attributes
- Definition Classes
- BIOCatsApplicative -> Apply
- Inherited from:
- BIOCatsApplicative
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Similar to map2 but uses Eval to allow for laziness in the F[B]
argument. This can allow for "short-circuiting" of computations.
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,
but map2Eval
"short-circuits" the computation. x
is None
and thus the
result of bomb
doesn't even need to be evaluated in order to determine
that the result of map2Eval
should be None
.
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
Attributes
- Definition Classes
- BIOCatsApplicative -> Apply
- Inherited from:
- BIOCatsApplicative
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
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))
Attributes
- Inherited from:
- FlatMap
A non-terminating effect that never completes, which causes a fiber to semantically block indefinitely. This is the purely functional, asynchronous equivalent of an infinite while loop in Java, but no native threads are blocked.
A non-terminating effect that never completes, which causes a fiber to semantically block indefinitely. This is the purely functional, asynchronous equivalent of an infinite while loop in Java, but no native threads are blocked.
A fiber that is suspended in never can be canceled if it is completely unmasked before it suspends:
// ignoring race conditions between `start` and `cancel`
F.never.start.flatMap(_.cancel) <-> F.unit
However, if the fiber is masked, cancellers will be semantically blocked forever:
// ignoring race conditions between `start` and `cancel`
F.uncancelable(_ => F.never).start.flatMap(_.cancel) <-> F.never
Attributes
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Registers a finalizer that is invoked if cancelation is observed during the evaluation of
fa
. If the evaluation of fa
completes without encountering a cancelation, the finalizer
is unregistered before proceeding.
Registers a finalizer that is invoked if cancelation is observed during the evaluation of
fa
. If the evaluation of fa
completes without encountering a cancelation, the finalizer
is unregistered before proceeding.
During finalization, all actively registered finalizers are run exactly once. The order by
which finalizers are run is dictated by nesting: innermost finalizers are run before
outermost finalizers. For example, in the following program, the finalizer f1
is run
before the finalizer f2
:
F.onCancel(F.onCancel(F.canceled, f1), f2)
If a finalizer throws an error during evaluation, the error is suppressed, and implementations may choose to report it via a side channel. Finalizers are always uncancelable, so cannot otherwise be interrupted.
Attributes
- fa
The effect that is evaluated after
fin
is registered.- fin
The finalizer to register before evaluating
fa
.- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Execute a callback on certain errors, then rethrow them. Any non matching error is rethrown as well.
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)))
Attributes
- Inherited from:
- ApplicativeError
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)
Attributes
- Definition Classes
- BIOCatsApplicative -> InvariantMonoidal
- Inherited from:
- BIOCatsApplicative
Combine an F[A]
and an F[B]
into an F[(A, B)]
that maintains the effects of both fa
and fb
.
Combine an F[A]
and an F[B]
into an F[(A, B)]
that maintains the effects of both fa
and fb
.
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))
Attributes
- Definition Classes
- FlatMap -> Apply -> Semigroupal
- Inherited from:
- FlatMap
Compose two actions, discarding any value produced by the second.
Compose two actions, discarding any value produced by the second.
Attributes
- 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.)
- Definition Classes
- BIOCatsApplicative -> Apply
- Inherited from:
- BIOCatsApplicative
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:
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)
Attributes
- Inherited from:
- FlatMap
Compose two actions, discarding any value produced by the first.
Compose two actions, discarding any value produced by the first.
Attributes
- 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.)
- Definition Classes
- BIOCatsApplicative -> Apply
- Inherited from:
- BIOCatsApplicative
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:
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)
Attributes
- Inherited from:
- FlatMap
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)
Attributes
- Definition Classes
- BIOCatsApplicative -> Applicative
- Inherited from:
- BIOCatsApplicative
Races the evaluation of two fibers that returns the result of the winner, except in the case of cancelation.
Races the evaluation of two fibers that returns the result of the winner, except in the case of cancelation.
The semantics of race are described by the following rules:
- If the winner completes with Outcome.Succeeded, the race returns the successful value. The loser is canceled before returning. 2. If the winner completes with Outcome.Errored, the race raises the error. The loser is canceled before returning. 3. If the winner completes with Outcome.Canceled, the race returns the result of the loser, consistent with the first two rules. 4. If both the winner and loser complete with Outcome.Canceled, the race is canceled. 8. If the race is masked and is canceled because both participants canceled, the fiber will block indefinitely.
Attributes
- fa
the effect for the first racing fiber
- fb
the effect for the second racing fiber
- See also:
raceOutcome for a variant that returns the outcome of the winner.
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Races the evaluation of two fibers that returns the Outcome of the winner. The winner of the race is considered to be the first fiber that completes with an outcome. The loser of the race is canceled before returning.
Races the evaluation of two fibers that returns the Outcome of the winner. The winner of the race is considered to be the first fiber that completes with an outcome. The loser of the race is canceled before returning.
Attributes
- fa
the effect for the first racing fiber
- fb
the effect for the second racing fiber
- See also:
race for a simpler variant that returns the successful outcome.
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
A low-level primitive for racing the evaluation of two fibers that returns the Outcome of the winner and the Fiber of the loser. The winner of the race is considered to be the first fiber that completes with an outcome.
A low-level primitive for racing the evaluation of two fibers that returns the Outcome of the winner and the Fiber of the loser. The winner of the race is considered to be the first fiber that completes with an outcome.
racePair is a cancelation-unsafe function; it is recommended to use the safer variants.
Attributes
- fa
the effect for the first racing fiber
- fb
the effect for the second racing fiber
- See also:
raceOutcome and race for safer race variants.
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
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)
Attributes
- Definition Classes
- BIOCatsMonadError -> ApplicativeError
- Inherited from:
- BIOCatsMonadError
Returns raiseError
when cond
is false, otherwise F.unit
Returns raiseError
when cond
is false, otherwise F.unit
Attributes
- Example:
val tooMany = 5 val x: Int = ??? F.raiseUnless(x < tooMany)(new IllegalArgumentException("Too many"))
- Inherited from:
- ApplicativeError
Returns raiseError
when the cond
is true, otherwise F.unit
Returns raiseError
when the cond
is true, otherwise F.unit
Attributes
- Example:
val tooMany = 5 val x: Int = ??? F.raiseWhen(x >= tooMany)(new IllegalArgumentException("Too many"))
- Inherited from:
- ApplicativeError
Recover from certain errors by mapping them to an A
value.
Recover from certain errors by mapping them to an A
value.
Attributes
- See also:
handleError to handle any/all errors.
recoverWith to recover from certain errors by mapping them to
F[A]
values.- Inherited from:
- ApplicativeError
Recover from certain errors by mapping them to an F[A]
value.
Recover from certain errors by mapping them to an F[A]
value.
Attributes
- See also:
handleErrorWith to handle any/all errors.
recover to recover from certain errors by mapping them to
A
values.- Definition Classes
- BIOCatsMonadError -> ApplicativeError
- Inherited from:
- BIOCatsMonadError
Returns a new value that transforms the result of the source,
given the recover
or map
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
or map
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.
Attributes
- 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
- See also:
MonadError.redeemWith, attempt and handleError
- Inherited from:
- ApplicativeError
Returns a new value that transforms the result of the source,
given the recover
or bind
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
or bind
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.
Attributes
- bind
is the function that gets to transform the source in case of success
- 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
- See also:
redeem, attempt and handleErrorWith
- Definition Classes
- BIOCatsMonadError -> MonadError
- Inherited from:
- BIOCatsMonadError
Given fa
and n
, apply fa
n
times to construct an F[List[A]]
value.
Given fa
and n
, apply fa
n
times to construct an F[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))
Attributes
- Inherited from:
- Applicative
Given fa
and n
, apply fa
n
times discarding results to return F[Unit].
Given fa
and n
, apply fa
n
times discarding results to return F[Unit].
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[Unit] =
| Applicative[Counter].replicateA_(5, getAndIncrement)
scala> getAndIncrement5.run(0).value
res0: (Int, Unit) = (5,())
Attributes
- Inherited from:
- Applicative
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)
Attributes
- Inherited from:
- MonadError
Indicates the default "root scope" semantics of the F
in question. For types which do
''not'' implement auto-cancelation, this value may be set to CancelScope.Uncancelable
,
which behaves as if all values F[A]
are wrapped in an implicit "outer" uncancelable
which cannot be polled. Most IO
-like types will define this to be Cancelable
.
Indicates the default "root scope" semantics of the F
in question. For types which do
''not'' implement auto-cancelation, this value may be set to CancelScope.Uncancelable
,
which behaves as if all values F[A]
are wrapped in an implicit "outer" uncancelable
which cannot be polled. Most IO
-like types will define this to be Cancelable
.
Attributes
- Inherited from:
- GenSpawn
A low-level primitive for starting the concurrent evaluation of a fiber. Returns a Fiber that can be used to wait for a fiber or cancel it.
A low-level primitive for starting the concurrent evaluation of a fiber. Returns a Fiber that can be used to wait for a fiber or cancel it.
start is a cancelation-unsafe function; it is recommended to use the safer variant, background, to spawn fibers.
Attributes
- fa
the effect for the fiber
- See also:
background for the safer, recommended variant
- Definition Classes
- BIOCatsSpawn -> GenSpawn
- Inherited from:
- BIOCatsSpawn
Keeps calling f
until a scala.util.Right[B]
is returned.
Keeps calling f
until a scala.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
.
Attributes
- Definition Classes
- BIOCatsMonad -> FlatMap
- Inherited from:
- BIOCatsMonad
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Attributes
- Inherited from:
- ApplyArityFunctions
Tuples the A
value in F[A]
with the supplied B
value, with the B
value on the left.
Tuples the A
value in F[A]
with the supplied B
value, with the B
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))
Attributes
- Inherited from:
- Functor
Tuples the A
value in F[A]
with the supplied B
value, with the B
value on the right.
Tuples the A
value in F[A]
with the supplied B
value, with the B
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))
Attributes
- Inherited from:
- Functor
Masks cancelation on the current fiber. The argument to body
of type Poll[F]
is a
natural transformation F ~> F
that enables polling. Polling causes a fiber to unmask
within a masked region so that cancelation can be observed again.
Masks cancelation on the current fiber. The argument to body
of type Poll[F]
is a
natural transformation F ~> F
that enables polling. Polling causes a fiber to unmask
within a masked region so that cancelation can be observed again.
In the following example, cancelation can be observed only within fb
and nowhere else:
F.uncancelable { poll =>
fa *> poll(fb) *> fc
}
If a fiber is canceled while it is masked, the cancelation is suppressed for as long as the fiber remains masked. Whenever the fiber is completely unmasked again, the cancelation will be respected.
Masks can also be stacked or nested within each other. If multiple masks are active, all masks must be undone so that cancelation can be observed. In order to completely unmask within a multi-masked region the poll corresponding to each mask must be applied to the effect, outermost-first.
F.uncancelable { p1 =>
F.uncancelable { p2 =>
fa *> p2(p1(fb)) *> fc
}
}
The following operations are no-ops:
- Polling in the wrong order
- Subsequent polls when applying the same poll more than once:
poll(poll(fa))
is equivalent topoll(fa)
- Applying a poll bound to one fiber within another fiber
Attributes
- body
A function which takes a Poll and returns the effect that we wish to make uncancelable.
- Definition Classes
- BIOCatsMonadCancel -> MonadCancel
- Inherited from:
- BIOCatsMonadCancel
Returns an F[Unit]
value, equivalent with pure(())
.
Returns an F[Unit]
value, equivalent with pure(())
.
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(())
Attributes
- Definition Classes
- Inherited from:
- BIOCatsApplicative
Returns the given argument (mapped to Unit) if cond
is false
,
otherwise, unit lifted into F.
Returns the given argument (mapped to Unit) if cond
is false
,
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()
Attributes
- Definition Classes
- BIOCatsApplicative -> Applicative
- Inherited from:
- BIOCatsApplicative
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.
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.
Attributes
- Inherited from:
- FlatMap
Execute an action repeatedly until the Boolean
condition returns true
.
The condition is evaluated after the loop body. Collects results into an
arbitrary Alternative
value, such as a Vector
.
This implementation uses append on each evaluation result,
so avoid data structures with non-constant append performance, e.g. List
.
Execute an action repeatedly until the Boolean
condition returns true
.
The condition is evaluated after the loop body. Collects results into an
arbitrary Alternative
value, such as a Vector
.
This implementation uses append on each evaluation result,
so avoid data structures with non-constant append performance, e.g. List
.
Attributes
- Inherited from:
- Monad
Execute an action repeatedly until the Boolean
condition returns true
.
The condition is evaluated after the loop body. Discards results.
Execute an action repeatedly until the Boolean
condition returns true
.
The condition is evaluated after the loop body. Discards results.
Attributes
- Inherited from:
- Monad
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))
Attributes
- Inherited from:
- Functor
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((), (), ())
Attributes
- Definition Classes
- BIOCatsFunctor -> Functor
- Inherited from:
- BIOCatsFunctor
Void any error, by mapping it to Unit
.
Void any error, by mapping it to Unit
.
This is useful when errors are reported via a side-channel but not directly handled. For example in Cats Effect:
IO.deferred[OutcomeIO[A]].flatMap { oc =>
ioa.guaranteeCase(oc.complete(_).void).void.voidError.start
// ...
}
Without the .voidError
, the Cats Effect runtime would consider an error in ioa
to be
unhandled and elevate it to ExecutionContext#reportFailure.
Attributes
- See also:
handleError to map to an
A
value instead ofUnit
.- Inherited from:
- ApplicativeError
Returns the given argument (mapped to Unit) if cond
is true
, otherwise,
unit lifted into F.
Returns the given argument (mapped to Unit) if cond
is true
, 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(())
Attributes
- Definition Classes
- BIOCatsApplicative -> Applicative
- Inherited from:
- BIOCatsApplicative
Execute an action repeatedly as long as the given Boolean
expression
returns true
. The condition is evaluated before the loop body.
Collects the results into an arbitrary Alternative
value, such as a Vector
.
This implementation uses append on each evaluation result,
so avoid data structures with non-constant append performance, e.g. List
.
Execute an action repeatedly as long as the given Boolean
expression
returns true
. The condition is evaluated before the loop body.
Collects the results into an arbitrary Alternative
value, such as a Vector
.
This implementation uses append on each evaluation result,
so avoid data structures with non-constant append performance, e.g. List
.
Attributes
- Inherited from:
- Monad
Execute an action repeatedly as long as the given Boolean
expression
returns true
. The condition is evaluated before the loop body.
Discards results.
Execute an action repeatedly as long as the given Boolean
expression
returns true
. The condition is evaluated before the loop body.
Discards results.
Attributes
- Inherited from:
- Monad
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 as map(identity)
, but
according to the functor laws, that should be equal to fa
, and a type
cast is often much more performant.
See this example
of widen
creating a ClassCastException
.
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)
Attributes
- Definition Classes
- BIOCatsFunctor -> Functor
- Inherited from:
- BIOCatsFunctor
Deprecated and Inherited methods
Attributes
- Deprecated
- true
- Inherited from:
- Apply