Packages

abstract class MVar2[F[_], A] extends MVar[F, A]

A mutable location, that is either empty or contains a value of type A.

It has the following fundamental atomic operations:

  • put which fills the var if empty, or blocks (asynchronously) until the var is empty again
  • tryPut which fills the var if empty. returns true if successful
  • take which empties the var if full, returning the contained value, or blocks (asynchronously) otherwise until there is a value to pull
  • tryTake empties if full, returns None if empty.
  • read which reads the current value without touching it, assuming there is one, or otherwise it waits until a value is made available via put
  • tryRead returns a variable if it exists. Implemented in the successor MVar2
  • swap takes a value, replaces it and returns the taken value. Implemented in the successor MVar2
  • isEmpty returns true if currently empty

The MVar is appropriate for building synchronization primitives and performing simple inter-thread communications. If it helps, it's similar with a BlockingQueue(capacity = 1), except that it doesn't block any threads, all waiting being done asynchronously (via Async or Concurrent data types, such as IO).

Given its asynchronous, non-blocking nature, it can be used on top of Javascript as well.

Inspired by Control.Concurrent.MVar from Haskell and by scalaz.concurrent.MVar.

The MVar2 is the successor of MVar with tryRead and swap. It was implemented separately only to maintain binary compatibility with MVar.

Annotations
@nowarn()
Source
MVar.scala
Linear Supertypes
MVar[F, A], MVarDocumentation, AnyRef, Any
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. MVar2
  2. MVar
  3. MVarDocumentation
  4. AnyRef
  5. Any
  1. Hide All
  2. Show All
Visibility
  1. Public
  2. Protected

Instance Constructors

  1. new MVar2()

Abstract Value Members

  1. abstract def isEmpty: F[Boolean]

    Returns true if the MVar is empty and can receive a put, or false otherwise.

    Returns true if the MVar is empty and can receive a put, or false otherwise.

    Note that due to concurrent tasks, logic built in terms of isEmpty is problematic.

    Definition Classes
    MVar
  2. abstract def modify[B](f: (A) => F[(A, B)]): F[B]

    Modifies the contents of the MVar using the effectful function f, but also allows for returning a value derived from the original contents of the MVar.

    Modifies the contents of the MVar using the effectful function f, but also allows for returning a value derived from the original contents of the MVar. Like use, in case of failure, it sets the contents of the MVar to the original value.

    f

    effectful function that operates on the contents of this MVar

    returns

    the second value produced by applying f to the contents of this MVar

    Note

    This operation is only safe from deadlocks if there are no other producers for this MVar.

  3. abstract def modify_(f: (A) => F[A]): F[Unit]

    Modifies the contents of the MVar using the effectful function f.

    Modifies the contents of the MVar using the effectful function f. Like use, in case of failure, it sets the contents of the MVar to the original value.

    f

    effectful function that operates on the contents of this MVar

    returns

    no useful value. Executed only for the effects.

    Note

    This operation is only safe from deadlocks if there are no other producers for this MVar.

  4. abstract def put(a: A): F[Unit]

    Fills the MVar if it is empty, or blocks (asynchronously) if the MVar is full, until the given value is next in line to be consumed on take.

    Fills the MVar if it is empty, or blocks (asynchronously) if the MVar is full, until the given value is next in line to be consumed on take.

    This operation is atomic.

    returns

    a task that on evaluation will complete when the put operation succeeds in filling the MVar, with the given value being next in line to be consumed

    Definition Classes
    MVar
  5. abstract def read: F[A]

    Tries reading the current value, or blocks (asynchronously) until there is a value available.

    Tries reading the current value, or blocks (asynchronously) until there is a value available.

    This operation is atomic.

    returns

    a task that on evaluation will be completed after a value has been read

    Definition Classes
    MVar
  6. abstract def swap(newValue: A): F[A]

    Replaces a value in MVar and returns the old value.

    Replaces a value in MVar and returns the old value.

    newValue

    is a new value

    returns

    the value taken

    Note

    This operation is only safe from deadlocks if there are no other producers for this MVar.

  7. abstract def take: F[A]

    Empties the MVar if full, returning the contained value, or blocks (asynchronously) until a value is available.

    Empties the MVar if full, returning the contained value, or blocks (asynchronously) until a value is available.

    This operation is atomic.

    returns

    a task that on evaluation will be completed after a value was retrieved

    Definition Classes
    MVar
  8. abstract def tryPut(a: A): F[Boolean]

    Fill the MVar if we can do it without blocking,

    Fill the MVar if we can do it without blocking,

    returns

    whether or not the put succeeded

    Definition Classes
    MVar
  9. abstract def tryRead: F[Option[A]]

    A non-blocking version of read.

    A non-blocking version of read.

    returns

    an Option holding the current value, None means it was empty

  10. abstract def tryTake: F[Option[A]]

    empty the MVar if full

    empty the MVar if full

    returns

    an Option holding the current value, None means it was empty

    Definition Classes
    MVar
  11. abstract def use[B](f: (A) => F[B]): F[B]

    Applies the effectful function f on the contents of this MVar.

    Applies the effectful function f on the contents of this MVar. In case of failure, it sets the contents of the MVar to the original value.

    f

    effectful function that operates on the contents of this MVar

    returns

    the value produced by applying f to the contents of this MVar

    Note

    This operation is only safe from deadlocks if there are no other producers for this MVar.

Concrete Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##: Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  5. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native() @HotSpotIntrinsicCandidate()
  6. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  7. def equals(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef → Any
  8. final def getClass(): Class[_ <: AnyRef]
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  9. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  10. def imapK[G[_]](f: ~>[F, G], g: ~>[G, F]): MVar2[G, A]

    Modify the context F using natural isomorphism f with g.

    Modify the context F using natural isomorphism f with g.

    f

    functor transformation from F to G

    g

    functor transformation from G to F

    returns

    MVar2 with a modified context G derived using a natural isomorphism from F

  11. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  12. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  13. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  14. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native() @HotSpotIntrinsicCandidate()
  15. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  16. def toString(): String
    Definition Classes
    AnyRef → Any
  17. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  18. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()
  19. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])

Deprecated Value Members

  1. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable]) @Deprecated
    Deprecated
  2. def mapK[G[_]](f: ~>[F, G]): MVar[G, A]

    Modify the context F using transformation f.

    Modify the context F using transformation f.

    Definition Classes
    MVar
    Annotations
    @deprecated
    Deprecated

    (Since version 2.2.0) mapK is deprecated in favor of imapK which supports the new invariant MVar2 interface

Inherited from MVar[F, A]

Inherited from MVarDocumentation

Inherited from AnyRef

Inherited from Any

Ungrouped