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Manual Reference Pages  - allocated (3fortran)

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NAME

ALLOCATED(3) - [ARRAY:INQUIRY] Allocation status of an allocatable entity

SYNOPSIS

result = allocated(array|scalar)

         logical function allocated(array,scalar)

          type(TYPE(kind=**)),allocatable,optional :: array(..)
          type(TYPE(kind=**)),allocatable,optional :: scalar

CHARACTERISTICS

o	a kind designated as ** may be any supported kind for the type
o	ARRAY may be any allocatable array object of any type.
o	SCALAR may be any allocatable scalar of any type.
o	the result is a default logical scalar

DESCRIPTION

ALLOCATED(3) checks the allocation status of both arrays and scalars.

At least one and only one of ARRAY or SCALAR must be specified.

OPTIONS

o	ENTITY : the allocatable object to test.

RESULT

If the argument is allocated then the result is .true.; otherwise, it returns .false..

EXAMPLES

Sample program:

    program demo_allocated
    use,intrinsic :: iso_fortran_env, only : dp=>real64,sp=>real32
    implicit none
    real(kind=sp), allocatable :: x(:)
    character(len=256) :: message
    integer :: istat
      ! basics
       if( allocated(x)) then
           write(*,*)’do things if allocated’
       else
           write(*,*)’do things if not allocated’
       endif

       ! if already allocated, deallocate
       if ( allocated(x) ) deallocate(x,STAT=istat, ERRMSG=message )
       if(istat.ne.0)then
          write(*,*)trim(message)
          stop
       endif

       ! only if not allocated, allocate
       if ( .not. allocated(x) ) allocate(x(20))

      ! allocation and intent(out)
       call intentout(x)
       write(*,*)’note it is deallocated!’,allocated(x)

       contains

       subroutine intentout(arr)
       ! note that if arr has intent(out) and is allocatable,
       ! arr is deallocated on entry
       real(kind=sp),intent(out),allocatable :: arr(:)
           write(*,*)’note it was allocated in calling program’,allocated(arr)
       end subroutine intentout

    end program demo_allocated

Results:

     >  do things if not allocated
     >  note it was allocated in calling program F
     >  note it is deallocated! F

STANDARD

Fortran 95. allocatable scalar entities were added in Fortran 2003.

SEE ALSO

MOVE_ALLOC(3)

fortran-lang intrinsic descriptions (license: MIT) @urbanjost

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Nemo Release 3.1

allocated (3fortran)

April 28, 2024

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