Add a function in Algo that states if the graph is directed

lib/algo/algo.ml

-(* Time-stamp: <modified the 07/10/2019 (at 15:02) by Erwan Jahier> *)
+(* Time-stamp: <modified the 17/10/2019 (at 21:09) by Erwan Jahier> *)
 
 open Sasacore
 (* Process programmer API *)
@@ -105,6 +105,7 @@ let mean_degree = Register.mean_degree
 let max_degree = Register.max_degree
 let is_cyclic = Register.is_cyclic
 let is_connected = Register.is_connected
+let is_directed = Register.is_directed
 let is_tree = Register.is_tree
 let height = Register.height
 let links_number = Register.links_number

lib/algo/algo.mli

-(* Time-stamp: <modified the 07/10/2019 (at 14:35) by Erwan Jahier> *)
+(* Time-stamp: <modified the 17/10/2019 (at 21:08) by Erwan Jahier> *)
 (** The Algorithm programming Interface.
 
     A SASA process is an instance of an algorithm defined via this
@@ -64,6 +64,7 @@ val card : unit -> int
 val min_degree : unit -> int
 val mean_degree : unit -> float
 val max_degree : unit -> int
+val is_directed : unit -> bool
 val is_cyclic : unit -> bool
 val is_connected : unit -> bool
 val is_tree : unit -> bool

lib/sasacore/register.ml

-(* Time-stamp: <modified the 07/10/2019 (at 10:00) by Erwan Jahier> *)
+(* Time-stamp: <modified the 17/10/2019 (at 21:08) by Erwan Jahier> *)
 
 type 's neighbor = {
   state:  's ;
@@ -29,6 +29,7 @@ type 's internal_tables = {
   mutable is_cyclic    : bool option;
   mutable is_connected : bool option;
   mutable is_tree      : bool option;
+  mutable is_directed  : bool option;
   mutable height       : (string -> int); 
   mutable links_number : int; 
   mutable diameter     : int;
@@ -39,6 +40,7 @@ type properties_functions = {
   mutable min_max             : unit -> int*int;
   mutable mean_deg            : unit -> float;
   mutable is_connected_cyclic : unit -> bool*bool;
+  mutable is_directed         : unit -> bool;
   mutable links_number        : unit -> int;
   mutable diameter            : unit -> int
 }
@@ -61,6 +63,7 @@ let (tbls:'s internal_tables) = {
   is_cyclic    = None;
   is_connected = None;
   is_tree      = None;
+  is_directed  = None;
   height       = (fun _ -> -1);
   links_number = (-1);
   diameter     = (-1)
@@ -71,6 +74,7 @@ let (prop_funs:properties_functions) = {
   min_max             = (fun () -> (-1,-1));
   mean_deg            = (fun () -> -1.);
   is_connected_cyclic = (fun () -> (false,false));
+  is_directed         = (fun () -> false);
   links_number        = (fun () -> -1);
   diameter            = (fun () -> -1)
 }
@@ -177,20 +181,33 @@ let set_connec_cycl : (unit -> unit) =
     tbls.is_connected <- Some x;
     tbls.is_cyclic <- Some y
 
-
-let (card : unit -> int) =
-  fun () -> match tbls.card with 
-  | -1 -> (let c = prop_funs.card () in tbls.card <- c; c)
+let (card : unit -> int) = fun () ->
+  match tbls.card with 
+  | -1 ->
+     let c = prop_funs.card () in
+     tbls.card <- c;
+     c
   | c -> c
 
+let (is_directed : unit -> bool) = fun () ->
+  match tbls.is_directed with 
+  | None ->
+     let c = prop_funs.is_directed () in
+     tbls.is_directed <- Some c;
+     c
+  | Some c -> c
+
 let (min_degree : unit -> int) = 
   fun () -> match tbls.min_deg with 
   | -1 -> (set_min_max (); tbls.min_deg)
   | m -> m
 
-let (mean_degree : unit -> float) = 
-  fun () -> match tbls.mean_deg with 
-  | -1. -> (let m = prop_funs.mean_deg () in tbls.mean_deg <- m; m)
+let (mean_degree : unit -> float) = fun () ->
+  match tbls.mean_deg with 
+  | -1. ->
+     let m = prop_funs.mean_deg () in
+     tbls.mean_deg <- m;
+     m
   | m -> m
 
 let (max_degree : unit -> int) = 
@@ -198,25 +215,30 @@ let (max_degree : unit -> int) =
   | -1 -> (set_min_max (); tbls.max_deg)
   | m -> m
 
-let (is_cyclic : unit -> bool) = 
-  fun () -> match tbls.is_cyclic with 
-  | None -> (set_connec_cycl (); 
-              match tbls.is_cyclic with 
-              | Some b -> b 
-              | _ -> assert false)
+let (is_cyclic : unit -> bool) = fun () ->
+  match tbls.is_cyclic with 
+  | None ->
+     set_connec_cycl (); 
+     (match tbls.is_cyclic with 
+      | Some b -> b 
+      | _ -> assert false)
   | Some b -> b
 
-let (is_connected : unit -> bool) = 
-  fun () -> match tbls.is_connected with 
-  | None -> (set_connec_cycl (); 
-              match tbls.is_connected with 
-              | Some b -> b 
-              | _ -> assert false)
+let (is_connected : unit -> bool) = fun () ->
+  match tbls.is_connected with 
+  | None -> (
+    set_connec_cycl (); 
+    match tbls.is_connected with 
+    | Some b -> b 
+    | _ -> assert false)
   | Some b -> b
 
-let (is_tree : unit -> bool) = 
-  fun () -> match tbls.is_tree with 
-  | None -> (let b = (not (is_cyclic ()) && (is_connected ())) in tbls.is_tree <- Some b; b)
+let (is_tree : unit -> bool) = fun () ->
+  match tbls.is_tree with 
+  | None ->
+     let b = (not (is_cyclic ()) && (is_connected ())) in
+     tbls.is_tree <- Some b;
+     b
   | Some b -> b
 
 (* Caution : this option is not the same as the option in the type tbls.height. 
@@ -229,14 +251,21 @@ let height : (unit -> (string -> int) option) =
 
 
 let (links_number : unit -> int) = 
-  fun () -> match tbls.links_number with 
-  | -1 -> (let n = prop_funs.links_number () in tbls.links_number <- n; n)
+  fun () ->
+  match tbls.links_number with 
+  | -1 ->
+     let n = prop_funs.links_number () in
+     tbls.links_number <- n;
+     n
   | n -> n
 
 let (diameter : unit -> int) = 
   fun () -> 
   match tbls.diameter with
-  | -1 -> (let d = (prop_funs.diameter ()) in tbls.diameter <- d; d)
+  | -1 ->
+     let d = (prop_funs.diameter ()) in
+     tbls.diameter <- d;
+     d
   | d -> d
   
 
@@ -244,6 +273,9 @@ let (diameter : unit -> int) =
 let set_card : ((unit -> int) -> unit) =
   fun f -> prop_funs.card <- f
 
+let set_is_directed : ((unit -> bool) -> unit) =
+  fun f -> prop_funs.is_directed <- f
+
 let set_degrees : ((unit -> int*int) -> unit) = 
   fun f -> prop_funs.min_max <- f
 

lib/sasacore/register.mli

-(* Time-stamp: <modified the 07/10/2019 (at 10:00) by Erwan Jahier> *)
+(* Time-stamp: <modified the 17/10/2019 (at 20:45) by Erwan Jahier> *)
 
 (** This module duplicates and extends the Algo module with get_*
    functions.
@@ -37,6 +37,7 @@ val max_degree : unit -> int
 val is_cyclic : unit -> bool
 val is_connected : unit -> bool
 val is_tree : unit -> bool
+val is_directed : unit -> bool
 
 (** If height () = None, then the graph doesn't have a height (because it isn't a tree)
    Otherwise, height () = Some h.*)
@@ -67,6 +68,7 @@ val set_card : (unit -> int) -> unit
 val set_degrees : (unit -> int*int) -> unit
 val set_mean_deg : (unit -> float) -> unit
 val set_is_connected_cyclic : (unit -> bool*bool) -> unit
+val set_is_directed : (unit -> bool) -> unit
 type node_id = string (* cf topology.mli *)
 val set_height : (node_id -> int) -> unit
 val set_links_number : (unit -> int) -> unit