# Fortran Wiki atomic_cas

## Description

atomic_cas compares the variable atom with the value of compare; if the value is the same, atom is set to the value of new. Additionally, old is set to the value of atom that was used for the comparison. When stat is present and the invocation was successful, it is assigned the value 0. If it is present and the invocation has failed, it is assigned a positive value; in particular, for a coindexed atom, if the remote image has stopped, it is assigned the value of iso_fortran_env‘s stat_stopped_image and if the remote image has failed, the value stat_failed_image.

## Standard

TS 18508 or later

## Class

Atomic subroutine

## Syntax

call atomic_cas (atom, old, compare, new [, stat])

## Arguments

• atom - Scalar coarray or coindexed variable of either integer type with atomic_int_kind kind or logical type with atomic_logical_kind kind.
• old - Scalar of the same type and kind as atom.
• compare - Scalar variable of the same type and kind as atom.
• new - Scalar variable of the same type as atom. If kind is different, the value is converted to the kind of atom.
• stat - (optional) Scalar default-kind integer variable.

## Example

program atomic
use iso_fortran_env
logical(atomic_logical_kind) :: atom[*], prev
call atomic_cas(atom[1], prev, .false., .true.))
end program atomic