Generic programming is a method for reusing a single piece in different contexts, such as with multiple data types. For example, the main body of a single numerical procedure can be reused for both single and double precision real variables or the code for a linked list can be reused for lists of integers, reals, or strings.
Generic programming is not available in Fortran 95 and it is only available in the form of parametrized user-defined types in Fortran 2003. However, the use of a preprocessor can assist with generic programming.
Some kinds of generic programming can be achieved using the transfer intrinsic, which copies bit patterns from one datatype to another without casting the value. Using this process, many data structures such as lists, stacks, queues, etc can be implemented by making the routines accept arrays of characters, and then using the transfer intrinsic to convert values before and after they are stored in the structure.
Here is an example of using the transfer intrinsic function to achieve simple generic data storage. The following code compiles with gfortran 4.6:
module data_mod implicit none private integer,parameter::N = 10 character,dimension(1),parameter::void = [achar(0)] type::data_t character,dimension(:),allocatable::d end type type(data_t),dimension(N)::data public::void public::set,get contains subroutine set(k,d) integer,intent(in)::k character,dimension(:),intent(in)::d if(allocated(data(k)%d)) deallocate(data(k)%d) allocate(data(k)%d(size(d))) data(k)%d = d end subroutine set function get(k) result(d) integer,intent(in)::k character,dimension(:),allocatable::d allocate(d(size(data(k)%d))) d = data(k)%d end function get end module data_mod program main use data_mod implicit none call set(1,transfer(10,void)) call set(2,transfer(10.0,void)) call set(3,transfer(10.0d0,void)) write(*,*) transfer(get(1),0) write(*,*) transfer(get(2),0.0) write(*,*) transfer(get(3),0.0d0) end program main
The output of the above code is as follows
10 10.000000 10.000000000000000
James Van Buskirk has written a generic version of BLAS available here: http://home.comcast.net/~kmbtib/Fortran_stuff/GENERIC_BLAS.ZIP