MVar

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
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.

Source: MVar.scala

Linear Supertypes

AnyRef, Any

Instance Constructors

new MVar()

Abstract Value Members

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.
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
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
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
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
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

Concrete Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def asInstanceOf[T0]: T0

Definition Classes
Any
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
def mapK[G[_]](f: ~>[F, G]): MVar[G, A]

Modify the context F using transformation f.
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

Related Docs: object MVar | package concurrent

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

Instance Constructors

new MVar()

Abstract Value Members

abstract def isEmpty: F[Boolean]

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

abstract def read: F[A]

abstract def take: F[A]

abstract def tryPut(a: A): F[Boolean]

abstract def tryTake: F[Option[A]]

Concrete Value Members

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

final def asInstanceOf[T0]: T0

def clone(): AnyRef

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

final def isInstanceOf[T0]: Boolean

def mapK[G[_]](f: ~>[F, G]): MVar[G, A]

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

Inherited from AnyRef

Inherited from Any

Ungrouped