Dear all, I discovered a problem in ublas identity_matrix class. I am doing linear algebra in finite fields. So my matrices contain no floats nor doubles. Instead I use some class that behaves like a number but does arithmetic in a finite field. Class instances are contructable by int, but _not_ default constructable by int. I don't want to have this. In matrix.hpp one finds the lines template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::zero_=0; template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::one_=1; These lines are problematic and the reason why my number class works not with the identity_matrix class. I think these lines should by changed into template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::zero_=T(0); template<class T> typename identity_matrix<T>::value_type identity_matrix<T>::one_=T(1); to make the ublas code more general. with regards Heiko -- -- Gute Sitten haben für die Gesellschaft mehr Wert als alle -- Berechnungen Newtons. (Friedrich II., der Große, 1712-1786) -- Supercomputing in Magdeburg @ http://tina.nat.uni-magdeburg.de -- Heiko Bauke @ http://www.uni-magdeburg.de/bauke