advice on package design

[spambox@volja.net]

Hello,
I've written a package for linked list operations for my personal use.
After a while I figured I'd write another package for some string
operations that I use frequently. On their own, they both work well.
Now comes the problem.
My string library uses my linked list library, which must be
instantiated -- the structure of a node must be supplied. After that,
the string library can use procedures from the linked list library. But
what about the end user? The linked list library defines a type, say
linked_list, and the string library instantiates it something like:

type word is record ...
package string_ll is new linkedlists(word);
use string_ll;

Ultimatelly, if some function from my strings package returns a
linked_list (as defined in the linked list package), it will be of the
type string_ll.linked_list, if we follow the above example. How could
it be available for further processing with routines from the linked
list package?

I could "use string_ll" (exactly as in the package) in my end program,
however that's probably a poor design, since the user need not know how
something was instantiated in another package.
If, on the other hand, I make another instance of linkedlist, I must
supply the same argument the string package does ("word" in the above
example), but then the resulting linked_list type would be
some_new_name.linked_list, which is not compatible with what the string
package uses (string_ll.linked_list in the example).

What is the correct way of dealing with such problems?

Thanks,

 andrej