1. 假设要声明一个scoped_ptr<Netflow>的变量，那么Netflow必须是一个complete type，这一点和定义普通指针Netflow *不同。所以使用scoped_ptr时，一般要include相应类的header file（#include "netflow.h"），而不能只靠forward declaration（class Netflow;）。具体原因和一种特殊情况见http://stackoverflow.com/questions/500656/c-using-scoped-ptr-as-a-member-variable Johannes Schaub的回帖 。下面是如果Netflow是incomplete type时，定义scoped_ptr<Netflow>时的g++编译错误信息：
/usr/include/boost/checked_delete.hpp: In function ‘void boost::checked_delete(T*) [with T = dpdet::Netflow<double>]’:
/usr/include/boost/smart_ptr/scoped_ptr.hpp:80:9: instantiated from ‘boost::scoped_ptr<T>::~scoped_ptr() [with T = dpdet::Netflow<double>]’
/host/Dropbox/projects/dpdet/detector/detector.h:29:14: instantiated from here
/usr/include/boost/checked_delete.hpp:32:58: error: invalid application of ‘sizeof’ to incomplete type ‘dpdet::Netflow<double>’
/usr/include/boost/checked_delete.hpp:32:58: error: creating array with negative size (‘-0x00000000000000001’)