static inline void copy(const F&& func, const EigenBase<Derived1>& in, EigenBase<Derived2>& out, size_t len=-1) { len = min(len, in.size()); assert(len <= out.size()); for (size_t i = 0; i < len; i++) { out(i) = in(i); } }
void print_size(const EigenBase<Derived>& b) { std::cout << "size (rows, cols): " << b.size() << " (" << b.rows() << ", " << b.cols() << ")" << std::endl; }