# Atomic.3o - Man Page

This module provides a purely sequential implementation of the concurrent atomic references provided by the Multicore OCaml standard library:

## Module

Module Atomic

## Documentation

Module **Atomic**

: **sig end**

This module provides a purely sequential implementation of the concurrent atomic references provided by the Multicore OCaml standard library:

https://github.com/ocaml-multicore/ocaml-multicore/blob/parallel_minor_gc/stdlib/atomic.mli

This sequential implementation is provided in the interest of compatibility: when people will start writing code to run on Multicore, it would be nice if their use of Atomic was backward-compatible with older versions of OCaml without having to import additional compatibility layers.

**Since** 4.12

*type* **'a** *t*

An atomic (mutable) reference to a value of type **'a** .

*val make* : **'a -> 'a t**

Create an atomic reference.

*val get* : **'a t -> 'a**

Get the current value of the atomic reference.

*val set* : **'a t -> 'a -> unit**

Set a new value for the atomic reference.

*val exchange* : **'a t -> 'a -> 'a**

Set a new value for the atomic reference, and return the current value.

*val compare_and_set* : **'a t -> 'a -> 'a -> bool**

**compare_and_set r seen v** sets the new value of **r** to **v** only if its current value is physically equal to **seen** -- the comparison and the set occur atomically. Returns **true** if the comparison succeeded (so the set happened) and **false** otherwise.

*val fetch_and_add* : **int t -> int -> int**

**fetch_and_add r n** atomically increments the value of **r** by **n** , and returns the current value (before the increment).

*val incr* : **int t -> unit**

**incr r** atomically increments the value of **r** by **1** .

*val decr* : **int t -> unit**

**decr r** atomically decrements the value of **r** by **1** .