Clojure LDC 5
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This document summarizes three Clojure functions for updating atoms and refs: reset! sets the value of an atom without regard for its current value and returns the new value; compare-and-set! atomically sets the value of an atom only if its current value matches the given old value, returning true if set or false if not; commute sets the in-transaction value of a ref by applying a function to its current value and commits by applying the function to the last committed value, allowing for more concurrency than ref-set.
![user=> (doc reset!)
-------------------------
([atom newval])
Sets the value of atom to newval without regard for the
current value. Returns newval.](https://image.slidesharecdn.com/clojurepres5-111115094353-phpapp02/85/Clojure-LDC-5-3-320.jpg)
![compare-and-set!
-------------------------
([atom oldval newval])
Atomically sets the value of atom to newval if and only if
the current value of the atom is identical to oldval. Returns
true if set happened, else false](https://image.slidesharecdn.com/clojurepres5-111115094353-phpapp02/85/Clojure-LDC-5-4-320.jpg)
![commute
-------------------------
([ref fun & args])
Must be called in a transaction. Sets the in-transaction-value of ref
to:
(apply fun in-transaction-value-of-ref args)
and returns the in-transaction-value of ref.
At the commit point of the transaction, sets the value of ref to be:
(apply fun most-recently-committed-value-of-ref args)
Thus fun should be commutative, or, failing that, you must accept
last-one-in-wins behavior. commute allows for more concurrency
than ref-set.](https://image.slidesharecdn.com/clojurepres5-111115094353-phpapp02/85/Clojure-LDC-5-5-320.jpg)
Clojure LDC 5
- 2. 3 clojures funcions Set - Rearrange reset! compare-and-set! commute
- 3. user=> (doc reset!) ------------------------- ([atom newval]) Sets the value of atom to newval without regard for the current value. Returns newval.
- 4. compare-and-set! ------------------------- ([atom oldval newval]) Atomically sets the value of atom to newval if and only if the current value of the atom is identical to oldval. Returns true if set happened, else false
- 5. commute ------------------------- ([ref fun & args]) Must be called in a transaction. Sets the in-transaction-value of ref to: (apply fun in-transaction-value-of-ref args) and returns the in-transaction-value of ref. At the commit point of the transaction, sets the value of ref to be: (apply fun most-recently-committed-value-of-ref args) Thus fun should be commutative, or, failing that, you must accept last-one-in-wins behavior. commute allows for more concurrency than ref-set.
- 7. partition-*