john Hi, in TC++PL3 on page 665, regarding valarray member functions, it is mentioned: "valarray operator-() const; // result[i]= -v[i] for every element // similarly: +, ~, !" I checked the web and could not find anything that explains the need of this "operator+". Any ideas? In MSDN it is mentioned: "Standard C++ Library Reference valarray::operator+ A unary operator that applies ...