passing pointer arguments in fortran

Question

I am wondering what is the proper way to write the following code?

PROGRAM foo

  INTEGER :: x
  REAL(KIND=8), TARGET, DIMENSION(0: 10) :: array
  REAL(KIND=8),          


        

Answer 1

It depends what you mean with "proper" way. As IanH already pointed out, you need an explicit interface (best done via packing things in a module) and using allocatables instead of pointers, if possible.

I'd further add, that if you do not want to change the allocation status of your array within your subroutine, but only want to manipulate its elements, then use a simple assumed shape array within your subroutine. Below you find a working example for it. A few more things to note:

• Do not use real(kind=8) as not all compilers use the number of bytes as kind for the real numbers. If you want double precision accuracy, ask for it explicitely as below.

• If you just want to fill up an array with a constant value, do it the simple way: array(:) = 2.0_dp

And here the example:

module accuracy
  implicit none

  integer, parameter :: dp = kind(1.0d0)

end module accuracy


module barmodule
  use accuracy
  implicit none

contains

  subroutine  bar(array)
    real(dp), intent(inout) :: array(:)

    integer :: ii

    do ii = 1, size(array)
      array(ii) = ii
    end do

  end subroutine bar

end module barmodule


program foo
  use accuracy
  use barmodule
  implicit none

  real(dp), dimension(0:10) :: array
  call bar(array)

end program foo