Using deferred bindings

[Ralph Kube]

Hello,
I am trying to compile fortran code that uses deferred bindings. The 
full code is listed in section A1 from this paper: 
http://portal.acm.org/citation.cfm?id=1644001.1644004.

It consists of 3 files, integrable_model.f03, lorenz.f03 and main.f03,
all 3 adhere to the fortran 2003 standard.

In integrable_model, An abstract type, integrable_model is defined
which contains the deferred procedures and defines new operators

module integrable_model_module
   type, abstract, public :: integrable_model
     contains
       procedure(time_derivative), deferred :: d_dt
       procedure(symmetric_operator), deferred    :: add
       procedure(symmetric_assignment), deferred  :: assign
       procedure(asymmetric_operator), deferred   :: multiply
       generic, public :: operator(+) => add
       generic, public :: operator(*) => multiply
       generic, public :: operator(=) => assign
     end type integrable_model
  ...
end module integrable_model_module

in the file integrable_model.f03

An integrable model is implemented in the file lorenz.f03
and extended with the lorenz type:

module lorenz_module
type, extends(integrable_model), public :: lorenz
   contains
     procedure, public :: d_dt => dLorenz_dt
     procedure, public :: add => add_lorenz
     procedure, public :: multiply => multiply_lorenz
     procudure, public :: assign => assign_lorenz
     ...
end type lorenz
  ...
end model lorenz_module


The code snippets above shows only the declaration of the deferred 
type-bound procedure bindings and omits the abstract interface 
declaration which is included in the file integrable_model.f03


Compiling and linking these files yields the following errors:

gfortran -fdefault-real-8  -std=f2003 -fno-underscoring  -Wall -c 
integrable_model.f03
gfortran -fdefault-real-8  -std=f2003 -fno-underscoring  -Wall -c lorenz.f03
gfortran -fdefault-real-8  -std=f2003 -fno-underscoring  -Wall 
-L/Users/ralph/source/design_patterns/lorenz 
-I/Users/ralph/source/design_patterns/lorenz  -o main integrable_model.o 
lorenz.o main.f03
Undefined symbols:
   "_symmetric_operator", referenced from:
       ___integrable_model_module_MOD_integrate in integrable_model.o
   "_symmetric_assignment", referenced from:
       _d_dt.1554 in integrable_model.o
       ___integrable_model_module_MOD_integrate in integrable_model.o
   "_asymmetric_operator", referenced from:
       ___integrable_model_module_MOD_integrate in integrable_model.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [main] Error 1


To me, it seems as if the module integrable_model would expect an 
implementation of the deferred type-bound procedures in the file 
integrable_model.f03. But the whole key of this program is that their 
actual implementation is deferred to the place, where the extended type 
implements them.

Do I see it correctly, that the linker is unaware that the actual 
implementation of symmetric_operator, symmetric_assignment and 
asymmetric_operator are not to be found in integrable_model.o ?


Cheers, Ralph