MVar2
A mutable location, that is either empty or contains a value of type 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 MVar2swap
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
.
Value members
Abstract methods
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.
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.
- Value Params
- f
effectful function that operates on the contents of this
MVar
- Returns
the second value produced by applying
f
to the contents of thisMVar
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar
.
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.
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.
- Value Params
- 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
.
Replaces a value in MVar and returns the old value.
Replaces a value in MVar and returns the old value.
- Value Params
- 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
.
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.
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.
- Value Params
- f
effectful function that operates on the contents of this
MVar
- Returns
the value produced by applying
f
to the contents of thisMVar
- Note
This operation is only safe from deadlocks if there are no other producers for this
MVar
.
Concrete methods
Inherited methods
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.
- Inherited from
- MVar
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 theMVar
, with the given value being next in line to be consumed- Inherited from
- MVar
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
- Inherited from
- MVar
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
- Inherited from
- MVar
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
- Inherited from
- MVar