robust code

source/tensor/XList.cpp

@@ -48,9 +48,9 @@ XList NULLList;
 XList::XList()
 {
     mem    = NULL;
-    maxNum = 0;
+    maxNum = 8;
     count  = 0;
-    items  = NULL;
+    items  = new void*[8];
     isIntList = false;
 }
 

source/tensor/XTensor.cpp

@@ -573,10 +573,11 @@ get the size of a given dimension
 int XTensor::GetDim(const int dim) const
 {
     CheckNTErrors(dim < order, "dimenision is out of range!");
+    CheckNTErrors(dim >= -order, "dimenision is out of range!");
     
     int d = dim;
     if(dim < 0)
-        d = order - 1;
+        d = order + dim;
 
     return dimSize[d];
 }