Folds over the error and value types of the ZRef.
Folds over the error and value types of the ZRef. This is a highly
polymorphic method that is capable of arbitrarily transforming the error
and value types of the ZRef. For most use cases one of the more specific
combinators implemented in terms of fold will be more ergonomic but this
method is extremely useful for implementing new combinators.
Folds over the error and value types of the ZRef, allowing access to the
state in transforming the set value.
Folds over the error and value types of the ZRef, allowing access to the
state in transforming the set value. This is a more powerful version of
fold but requires unifying the error types.
Reads the value from the ZRef.
Writes a new value to the ZRef, with a guarantee of immediate consistency
(at some cost to performance).
Writes a new value to the ZRef without providing a guarantee of immediate
consistency.
Maps and filters the get value of the ZRef with the specified partial
function, returning a ZRef with a get value that succeeds with the
result of the partial function if it is defined or else fails with None.
Transforms the set value of the ZRef with the specified function.
Transforms the set value of the ZRef with the specified fallible
function.
Transforms both the set and get values of the ZRef with the specified
functions.
Transforms both the set and get values of the ZRef with the specified
fallible functions.
Transforms both the set and get errors of the ZRef with the specified
functions.
Filters the set value of the ZRef with the specified predicate,
returning a ZRef with a set value that succeeds if the predicate is
satisfied or else fails with None.
Filters the get value of the ZRef with the specified predicate,
returning a ZRef with a get value that succeeds if the predicate is
satisfied or else fails with None.
Transforms the get value of the ZRef with the specified function.
Transforms the get value of the ZRef with the specified fallible
function.
Returns a read only view of the ZRef.
Returns a write only view of the ZRef.
A
ZRef[RA, RB, EA, EB, A, B]is a polymorphic, purely functional description of a mutable reference. The fundamental operations of aZRefaresetandget.settakes a value of typeAand sets the reference to a new value, requiring an environment of typeRAand potentially failing with an error of typeEA.getgets the current value of the reference and returns a value of typeB, requiring an environment of typeRBand potentially failing with an error of typeEB.When the error and value types of the
ZRefare unified, that is, it is aZRef[R, R, E, E, A, A], theZRefalso supports atomicmodifyandupdateoperations. All operations are guaranteed to be safe for concurrent access.By default,
ZRefis implemented in terms of compare and swap operations for maximum performance and does not support performing effects within update operations. If you need to perform effects within update operations you can create aZRef.Synchronized, a specialized type ofZRefthat supports performing effects within update operations at some cost to performance. In this case writes will semantically block other writers, while multiple readers can read simultaneously.ZRef.Synchronizedalso supports composing multipleZRef.Synchronizedvalues together to form a singleZRef.Synchronizedvalue that can be atomically updated using thezipoperator. In this case reads and writes will semantically block other readers and writers.NOTE: While
ZRefprovides the functional equivalent of a mutable reference, the value inside theZRefshould normally be immutable since compare and swap operations are not safe for mutable values that do not support concurrent access. If you do need to use a mutable valueZRef.Synchronizedwill guarantee that access to the value is properly synchronized.