include "tree.mzn";
include "subgraph.mzn";  

predicate fzn_dpath(int: N, int: E, array[int] of int: from, array[int] of int: to,
                    var int: s, var int: t, array[int] of var bool: ns, array[int] of var bool: es) =
   dtree(N,E,from,to,s,ns,es) /\
   dtree(N,E,to,from,t,ns,es);

%-----------------------------------------------------------------------------%