minus index

source/tensor/XList.cpp

@@ -208,8 +208,12 @@ void XList::Insert(int pos, void * item)
 /* get the item at position i */
 void * XList::GetItem(int i) const
 {
-    CheckNTErrors(i >= 0 && i < count, "Index of a list item is out of scope!");
-    return items[i];
+    CheckNTErrors(i >= -1 && i < count, "Index of a list item is out of scope!");
+    CheckNTErrors(count > 0, "Cannt index the item in an empty list!");
+    if(i == -1)
+        return items[count - 1];
+    else
+        return items[i];
 }
 
 /* get the integer-typed item at position i */