function interface question

From: Helge Avlesen (avle_at_tindved.ii.uib.no)
Date: 02/23/05 

Date: Wed, 23 Feb 2005 13:29:56 +0100

Hi,
I have an array of a derived type object, where the object contains
pointers to different kinds of basic data types, e.g. arrays of
various dimensions. I would like to have a convenient interface to
fish pointers out of this list, so I tried to make a generic function,
but meet problems...

is it possible, in a "standard" way, to create a generic function from
functions with identical argument list, but different return type?
all compilers I have access to reject the below snippet because they
fail to see the difference between the functions (I guess). on the
other hand compilers seem happy if I return the pointer through the
argument list of a subroutine instead, but I do not really see why
this is easier to swallow for the compiler compared to checking the
return type of the function as below? 

-- 
Helge
module arraylist
  type array_element
     real, pointer, dimension(:) :: ptr1d
     real, pointer, dimension(:,:) :: ptr2d
  end type array_element
  type hlist
     integer last
     type(array_element), pointer :: item(:) => null()
  end type hlist
  interface list_get
     module procedure get_item1d, get_item2d
  end interface
  
contains
  
  function get_item1d(list,wanted_n)
    implicit none
    real, pointer, dimension(:) :: get_item1d
    type(hlist) :: list
    integer, optional :: wanted_n
    integer n
    n=list%last
    if(present(wanted_n))n=wanted_n    
    get_item1d => list%item(n)%ptr1d
  end function get_item1d  
  function get_item2d(list,wanted_n)
    implicit none
    real, pointer, dimension(:,:) :: get_item2d
    type(hlist) :: list
    integer, optional :: wanted_n
    integer n
    n=list%last
    if(present(wanted_n))n=wanted_n    
    get_item2d => list%item(n)%ptr2d
  end function get_item2d
  
end module arraylist

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