fortran subroutine: array of arbitrary type

Question

I'm trying to write a subroutine to reverse the rows of an array. The following works, but explicitly declares the type of its input arr. Thus I'd need a separate subroutine to do the same thing for an array of type real. Surely there's a way to make it accept an array of arbitrary type - could someone help me with the syntax? Thanks!

SUBROUTINE flipud(arr)

    integer, dimension(:,:), intent(inout) :: arr
    integer, dimension(:,:), allocatable :: tmp
    integer i, j, nrow, ncol, ierr

    nrow = size(arr, 1)
    ncol = size(arr, 2)

    allocate(tmp(nrow, ncol), STAT=ierr)

    tmp(:,:) = arr(nrow:1:-1, :)
    arr = tmp
    deallocate(tmp)

END SUBROUTINE flipud

Agreed. Why introduce an extra layer of abstraction for such a simple task. — Raul Laasner
– Raul Laasner, Commented Dec 22, 2014 at 20:58
@VladimirF , point taken. You can probably tell Fortran isn't my strong suit. I was actually doing it that way and it wasn't working and I wondered if the syntax didn't work the way I thought it did. (This is actually part of a larger problem in which I'm parsing an ascii file but it's ending up upside down or transposed or something and I'm trying to debug; that must have been caused by a different problem...) Anyway, thanks; I've made the change. — Timothy W. Hilton
– Timothy W. Hilton, Commented Dec 22, 2014 at 22:55
If you're reading the elements of an array one at a time don't be surprised if Fortran fills the array column-by-column rather than row-by-row. And perhaps next time ask a question about what your problem really is, rather than about fixing a solution to it. — High Performance Mark
– High Performance Mark, Commented Dec 22, 2014 at 23:28

Fortranner · Accepted Answer · 2014-12-22 21:18:05Z

1

Fortran does not have the equivalent of C++ templates. You can create an interface with module procedures, as sketched below. The code that is common to both subroutines could be placed in a file that is incorporated using the INCLUDE statement.

module foo
interface fliupud
   module procedure flipud_i,flipud_r
end interface flipud

contains
subroutine flipud_i(arr)
integer, dimension(:,:), intent(inout) :: arr
! body
end subroutine flipud_i
!
subroutine flipud_r(arr)
real, dimension(:,:), intent(inout) :: arr
! body
end subroutine flipud_r
end module foo

answered Dec 22, 2014 at 21:18

Fortranner

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High Performance Mark Over a year ago

Yes, but why ? And what would you suggest for body that @VladimirF's comment above doesn't already encompass ?

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