> I was using the possibity of defining recursive types for developing a
> rather convoluted search in two coupled domains, but now I find that I
> cannot anymore... Has anybody found a(n elegant, concise) way of
> circumventing it... Please note that the type recursion is ended by
> inserting appropriate non-recursive variants... Maybe I abused the type
> system! (Note also that a recursion at the level of structures would be
> heaven sent!)

>     type p_state
[...]
>     and p = (p_label, p_state, s) node
>     and s = (s_label, s_state, p) node

You can change your type definitions as follow, and modify the
remaining of your program accordingly.

     type p_state
[...]
     and p = P of (p_label, p_state, s) node
     and s = S of (s_label, s_state, p) node

-- Jerome