overload of +

source/tensor/XTensor.cpp

@@ -460,7 +460,7 @@ XTensor XTensor::operator+ (const XTensor& tensor)
 }
 
 /* overloading of the plus-sign */
-XTensor XTensor::operator+ (const DTYPE shift)
+XTensor XTensor::operator+ (const DTYPE shift) const 
 {
     return ScaleAndShift(*this, 1, shift);
 }

source/tensor/XTensor.h

@@ -225,7 +225,7 @@ public:
     XTensor  operator+ (const XTensor &tensor);
     
     /* overloading of the plus-sign */
-    XTensor  operator+ (const DTYPE shift);
+    XTensor  operator+ (const DTYPE shift) const;
 
     /* overloading of the multiply-sign */
     XTensor  operator* (const XTensor &tensor);