event_query in Fortran Wiki

## Description

`event_query` assignes the number of events to `count` which have been
posted to the `event` variable and not yet been removed by calling
`event wait`. 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 and `count` is
assigned the value $-1$.

## Standard

[[TS 18508]] or later

## Class

Subroutine

## Syntax

~~~~~~~~~~~~~~~~~~~ {: lang=fortran }
call event_query(event, count [, stat])
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

## Arguments

- `event` - (`intent(in)`) Scalar of type `event_type`, defined in
  `iso_fortran_env`; shall not be coindexed.
- `count` - (`intent(out)`)Scalar integer with at least the precision of
   default integer.
- `stat` - (`optional`) Scalar default-kind integer variable.

## Example

~~~~~~~~~~~~~~~~~~~ {: lang=fortran }
program atomic
  use iso_fortran_env
  implicit none
  type(event_type) :: event_value_has_been_set[*]
  integer :: cnt
  if (this_image() == 1) then
    call event_query(event_value_has_been_set, cnt)
    if (cnt > 0) write(*,*) "Value has been set"
  elseif (this_image() == 2) then
    event post(event_value_has_been_set[1])
  end if
end program atomic
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

category: intrinsics