- "\tUnable to add "^ (string_of_arc arc) ^ " cause " ^
- (string_of_universe node1) ^ " is in the " ^
- closure_type ^ " closure {" ^
- (string_of_universe_set closure) ^ "} of " ^
- (string_of_universe node2) ^ "\n\n" ^
+ " Unable to add\n" ^
+ "\t" ^ (string_of_arc arc) ^ "\n" ^
+ " cause\n" ^
+ "\t" ^ (string_of_universe node1) ^ "\n" ^
+ " is in the " ^ closure_type ^ " closure\n" ^
+ "\t{" ^ (string_of_universe_set closure) ^ "}\n" ^
+ " of\n" ^
+ "\t" ^ (string_of_universe node2) ^ "\n\n" ^