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[helm.git] / components / extlib / hTopoSort.ml

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+(* Copyright (C) 2006, HELM Team.
+ * 
+ * This file is part of HELM, an Hypertextual, Electronic
+ * Library of Mathematics, developed at the Computer Science
+ * Department, University of Bologna, Italy.
+ * 
+ * HELM is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ * 
+ * HELM is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with HELM; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA  02111-1307, USA.
+ * 
+ * For details, see the HELM World-Wide-Web page,
+ * http://helm.cs.unibo.it/
+ *)
+
+module Make (OT:Map.OrderedType) =
+    struct
+      
+      module M = Map.Make(OT);;
+      
+      let topological_sort l find_deps = 
+        let find_deps m x = 
+          let deps = find_deps x in
+          M.add x deps m
+        in
+        (* build the partial order relation *)
+        let m = List.fold_left (fun m i -> find_deps m i) M.empty l in
+        let m = (* keep only deps inside l *) 
+          List.fold_left 
+            (fun m' i ->
+              M.add i (List.filter (fun x -> List.mem x l) (M.find i m)) m') 
+            M.empty l 
+        in
+        let m = M.map (fun x -> Some x) m in
+        (* utils *)
+        let keys m = M.fold (fun i _ acc -> i::acc) m [] in
+        let split l m = List.filter (fun i -> M.find i m = Some []) l in
+        let purge l m = 
+          M.mapi 
+            (fun k v -> if List.mem k l then None else 
+               match v with
+               | None -> None
+               | Some ll -> Some (List.filter (fun i -> not (List.mem i l)) ll)) 
+            m
+        in
+        let rec aux m res = 
+            let keys = keys m in
+            let ok = split keys m in
+            let m = purge ok m in
+            let res = ok @ res in
+            if ok = [] then res else aux m res
+        in
+        let rc = List.rev (aux m []) in
+        rc
+      ;;
+      
+    end
+;;
+