On Feb 2, 12:36 am, Ken <ken.al...@sbcglobal.net> wrote:

Yes, one passes the address of the procedure. By contrast, with
procedure pointers, you pass the address of the pointer variable,
which contains the address of the procedure. Example usage:

module m
  subroutine p()
     print *, 'Hello'
  end subroutine p
  subroutine foo (f, g)
      procedure() :: f
      procedure(), pointer :: g
      call f()
      call g()
   end subroutine foo
end module m

program test
  use m
  procedure(), pointer :: proc_ptr
  proc_ptr => p
  call foo (p, proc_ptr)
end program test

Here, "p" is the passed procedure, "proc_ptr" is a pointer variable,
which contains the address of "p".

Note that Equivalent to using
  procedure() :: f
the following:
  external f

A better choise is to use:
  procedure(p) :: f
  procedure(p), pointer :: g
Then the interface is known to the compiler. The first line is
equivalent to
  interface
    subroutine f()
    end subroutine f
  end interface

The other line is equivalent to the following, but I think not all
compilers support it:
  interface
    subroutine g()
    end subroutine g
  end interface
  pointer :: g

The procedure statement - and procedure pointers - are Fortran 2003
features. By now, most compilers have implemented it. I know that
gfortran supports it (full support since 4.5). Also g95 supports it
since years, though it does not seem to support the last version.

Tobias