Here's a bit of code that I believe is standard conforming
but that one compiler (I don't trust) finds an error in:

module intent_error
contains

  subroutine apply_double (x)
    real, intent(inout) :: x
    call apply_proc (x, double) ! (*) ERROR HERE
  end subroutine apply_double

  subroutine double (x)
    real, intent(inout) :: x
    x = 2.0 * x
  end subroutine double

  subroutine apply_proc (x, proc)
    real :: x  ! No intent; depends on proc
    interface
      subroutine proc (y)
        real :: y  ! (**) No intent, but can fix by supplying it.
      end subroutine proc
    end interface
    call proc (x)
  end subroutine apply_proc

end module intent_error

The compiler complains that there is an argument type/rank
mismatch at line (*).  If on line (**) I provide the the
same intent as for the procedure "double" then the error
goes away.  Is my code standard conforming?  I think so but
I'm no expert in these subtleties so I'm turning to the list!

This is the background for this example.  I want to perform
various operations on the data at each node in a binary tree.
Rather than replicate the code to traverse the tree for each
operator, I write a single procedure to traverse the tree that
applies a dummy procedure to the data at each node.  In this way
the operators can be simple procedures that know nothing about
binary trees.  As a result, though, it is impossible to specify
the intent of the dummy argument of the traversing procedure
(apply_proc above) or of the dummy argument of the dummy
procedure (line (**) above) as this depends entirely on behavior
of the actual procedure argument.

Thanks in advance for your help.

  Neil

-- 
Neil Carlson                                Voice: 505-665-1220
Motorola Computational Materials Group      FAX:   505-665-5757
Los Alamos National Laboratory              [log in to unmask]
Mailstop B221, Los Alamos, NM 87545         [log in to unmask]


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