Added program argument --ts to specify back actions

Transition.py

@@ -4,12 +4,11 @@ from Util import isEmpty
 
 ################################################################################
 class Transition :
-  available = set({"RIGHT", "LEFT", "SHIFT", "REDUCE", "EOS", "BACK 2"})
+  available = lambda self,x: x in {"RIGHT", "LEFT", "SHIFT", "REDUCE", "EOS"} or ("BACK" in x and len(x.split()) == 2)
 
   def __init__(self, name) :
-    if name not in self.available :
-      print("'%s' is not a valid transition type."%name, file=sys.stdout)
-      exit(1)
+    if not self.available(name) :
+      raise(Exception("'%s' is not a valid transition type."%name))
     self.name = name
 
   def __lt__(self, other) :

main.py

@@ -36,6 +36,8 @@ if __name__ == "__main__" :
     help="Print debug infos on stderr.")
   parser.add_argument("--silent", "-s", default=False, action="store_true",
     help="Don't print advancement infos.")
+  parser.add_argument("--ts", default="",
+    help="Comma sepaarated list of supplementary transitions. Example \"BACK 1,BACK 2\"")
   args = parser.parse_args()
 
   if args.debug :
@@ -51,7 +53,7 @@ if __name__ == "__main__" :
   if args.bootstrap is not None :
     args.bootstrap = int(args.bootstrap)
 
-  transitionSet = [Transition(elem) for elem in ["RIGHT", "LEFT", "SHIFT", "REDUCE", "BACK 2"]]
+  transitionSet = [Transition(elem) for elem in (["SHIFT","REDUCE","LEFT","RIGHT"]+args.ts.split(',')) if len(elem) > 0]
   strategy = {"RIGHT" : 1, "SHIFT" : 1, "LEFT" : 0, "REDUCE" : 0}
 
   if args.mode == "train" :