fix: exit with a gentle message whe the algo firls is empty

lib/sasacore/main.ml

-(* Time-stamp: <modified the 06/03/2020 (at 13:22) by Erwan Jahier> *)
+(* Time-stamp: <modified the 12/03/2020 (at 16:55) by Erwan Jahier> *)
 
 open Register
 
@@ -152,7 +152,7 @@ let (get_outputs_rif_decl: SasArg.t -> 'v Process.t list -> (string * string) li
   let vars =
     List.fold_left
       (fun acc p ->
-        let l = SasaState.to_rif_decl p.pid p.init in
+        let l = List.rev (SasaState.to_rif_decl p.pid p.init) in
         List.fold_left (fun acc (n,t) -> (n, Data.type_to_string t)::acc) acc l
       )
       vars
@@ -171,15 +171,15 @@ let (make : bool -> string array -> 'v t) =
   fun dynlink argv ->
   let args = 
     try SasArg.parse argv;
-	 with
-	   Failure(e) ->
-	    output_string stdout e;
-	    flush stdout ;
-	    exit 2
-	 | e ->
-	    output_string stdout (Printexc.to_string e);
-	    flush stdout;
-	    exit 2
+    with
+      Failure(e) ->
+      output_string stdout e;
+      flush stdout ;
+      exit 2
+    | e ->
+      output_string stdout (Printexc.to_string e);
+      flush stdout;
+      exit 2
   in
   try
     let dynlink = if args.output_algos then false else dynlink in
@@ -221,7 +221,7 @@ let (make : bool -> string array -> 'v t) =
     Register.set_is_directed (fun () -> g.directed);
 
     Register.verbose_level := args.verbose;
-    
+
     if !Register.verbose_level > 1 then Printf.eprintf "==> nodes: %s\n" nstr;
 
     if dynlink then (
@@ -232,16 +232,20 @@ let (make : bool -> string array -> 'v t) =
     ) else ();
 
     let initl = List.map (fun n ->
-                    let algo_id = Filename.chop_suffix n.Topology.file ".ml" in
-                    let value_of_string_opt = Register.get_value_of_string () in
-                    if value_of_string_opt = None || n.Topology.init = "" then
-                      Register.get_init_state algo_id (List.length (g.succ n.id)) n.id
-                    else
-                      match value_of_string_opt with
-                      | None -> assert false (* sno *)
-                      | Some f -> f n.Topology.init 
-                  )
-                  nl
+        if n.Topology.file = "" then (
+        Printf.eprintf " [sasa] Empty algo attribute in %s.\n%!" dot_file;
+        exit 1
+        );
+        let algo_id = Filename.chop_suffix n.Topology.file ".ml" in
+        let value_of_string_opt = Register.get_value_of_string () in
+        if value_of_string_opt = None || n.Topology.init = "" then
+          Register.get_init_state algo_id (List.length (g.succ n.id)) n.id
+        else
+          match value_of_string_opt with
+          | None -> assert false (* sno *)
+          | Some f -> f n.Topology.init 
+      )
+        nl
     in
 
     if !Register.verbose_level > 0 then Printf.eprintf "==> get_neighors\n";
@@ -303,11 +307,11 @@ let (make : bool -> string array -> 'v t) =
     args, pl_n, e
   with
   | Dynlink.Error e ->
-     Printf.eprintf " [sasa] Error when dynlinking (Sasacore.make): %s\n%!"
-       (Dynlink.error_message e);
-     flush_all();
-     exit 2
+    Printf.eprintf " [sasa] Error when dynlinking (Sasacore.make): %s\n%!"
+      (Dynlink.error_message e);
+    flush_all();
+    exit 2
   | e ->
-     Printf.eprintf " [sasa] Error (Sasacore.make): %s\n%!" (Printexc.to_string e);
-     flush_all();
-     exit 2
+    Printf.eprintf " [sasa] Error (Sasacore.make): %s\n%!" (Printexc.to_string e);
+    flush_all();
+    exit 2