Implemented some enhancement request and fixed some bugs

Fixed #2 : Variables are not recognized when inside a rule token
Fixed #15 : Rule: rete attributes are lost when a new ontology is created
Fixed #14 : ReteNetwork: Format rules must not be added to Rete network
Fixed #16 : DefConcept: Variables are not recognized when they are keyword arguments
Fixed #4 : Comparison are not correctly set when comparison property is a concept
Fixed #14 : Parser: merge FunctionParser.NamesNode and ExpressionParser.NamesNode
Fixed #18 : Parser: Add SourceCodeNode test to UnrecognizedNodeParser
Fixed #20 : At startup Number concept is saved in db a numerous number of time
Fixed #21 : CacheManager: I can remove all elements from a ListIfNeededCache and fill it again
Fixed #22 : CacheManager: I can remove all elements from a SetCache and fill it again
Fixed #23 : HistoryManager: history() no longer works
Fixed #24 : HistoryManager: history() no longer works after creating an exec rule
Fixed #25 : SheerkaMemory: Use MemoryObject instead of sheerka.local
Fixed #26 : Debugger: add the list all available services..
Fixed #27 : CONCEPTS_GRAMMARS_ENTRY does not seems to be in use any more
Fixed #28 : Give order to services

src/core/sheerka/services/SheerkaMemory.py

@@ -31,6 +31,7 @@ class SheerkaMemory(BaseService):
         self.sheerka.bind_service_method(self.add_to_memory, True, visible=False)
         self.sheerka.bind_service_method(self.add_many_to_short_term_memory, True, visible=False)
         self.sheerka.bind_service_method(self.get_from_memory, False)
+        self.sheerka.bind_service_method(self.get_last_from_memory, False)
         self.sheerka.bind_service_method(self.register_object, True, visible=False)
         self.sheerka.bind_service_method(self.unregister_object, True, visible=False)
         self.sheerka.bind_service_method(self.commit_registered_objects, True, visible=False)
@@ -39,7 +40,7 @@ class SheerkaMemory(BaseService):
 
         cache = ListIfNeededCache().auto_configure(self.OBJECTS_ENTRY)
         self.sheerka.om.register_cache(self.OBJECTS_ENTRY, cache, persist=True, use_ref=True)
-        
+
         self.sheerka.subscribe(EVENT_CONTEXT_DISPOSED, self.remove_context)
 
     def reset(self):
@@ -94,6 +95,21 @@ class SheerkaMemory(BaseService):
         :param concept:
         :return:
         """
+        last = self.sheerka.om.get(SheerkaMemory.OBJECTS_ENTRY, key)
+        if last is NotFound:
+            self.sheerka.om.put(SheerkaMemory.OBJECTS_ENTRY, key, MemoryObject(context.event.get_digest(), concept))
+            return
+        
+        if not isinstance(last, list) and last.obj == concept:
+            self.sheerka.om.delete(SheerkaMemory.OBJECTS_ENTRY, key, last)
+            self.sheerka.om.put(SheerkaMemory.OBJECTS_ENTRY, key, MemoryObject(context.event.get_digest(), concept))
+            return
+            
+        if isinstance(last, list) and last[-1].obj == concept:
+            self.sheerka.om.delete(SheerkaMemory.OBJECTS_ENTRY, key, last[-1])
+            self.sheerka.om.put(SheerkaMemory.OBJECTS_ENTRY, key, MemoryObject(context.event.get_digest(), concept))
+            return
+
         self.sheerka.om.put(SheerkaMemory.OBJECTS_ENTRY, key, MemoryObject(context.event.get_digest(), concept))
 
     def get_from_memory(self, context, key):
@@ -101,6 +117,20 @@ class SheerkaMemory(BaseService):
         """
         return self.sheerka.om.get(SheerkaMemory.OBJECTS_ENTRY, key)
 
+    def get_last_from_memory(self, context, key):
+        """
+        Return an object from memory
+        When there are multiple items, returns the last one
+        """
+        res = self.sheerka.om.get(SheerkaMemory.OBJECTS_ENTRY, key)
+        if res is NotFound:
+            return res
+
+        if isinstance(res, list):
+            return res[-1]
+
+        return res
+
     def register_object(self, context, key, concept):
         """
         Before adding memory_objects to memory, they first need to be registered
@@ -114,6 +144,8 @@ class SheerkaMemory(BaseService):
         :param concept:
         :return:
         """
+        if self.sheerka.during_initialisation:
+            return
         self.registration[key] = concept
 
     def unregister_object(self, context, key):