[Boost-users] [multi_array] Why the precondition on assignment?

Hello, I wonder if anyone can give me the rationale behind boost::multi_index's assignment operator having the following precondition: std::equal(this->shape(),this->shape()+this->num_dimensions(),x.shape()); as mentioned in this document: http://www.boost.org/doc/libs/1_38_0/libs/multi_array/doc/reference.html ? I've got a multi_array as a data member of a class and would like to avoid having to create an assignment operator for my class do the resizing and assignment. Regards, Peter Barker