message: clarifiation regarding non-commutative multiplication
diff: @@ -663,6 +663,11 @@ Elementary Arithmetic Operators
  Binary multiplication operator.
  +.. cpp:function:: template <typename Array> Array& operator*=(Array& x, Array y)
  +
  + Compound assignment operator for multiplication. Concerning ``Array`` types
  + with non-commutative multiplication: the operation expands to ``x = x * y;``.
  +
  .. cpp:function:: template <typename Array> Array mulhi(Array x, Array y)
  Returns the high part of an integer multiplication. For 32-bit scalar
  