Boost–progress_timer

#include <iostream>
#include<boost/progress.hpp>
#include <boost/static_assert.hpp>
using namespace std;
using namespace boost;


template<int N=2>
class new_progress_timer :public timer{
public:
	new_progress_timer(ostream &os=cout):m_os(os){
		
		BOOST_STATIC_ASSERT(N>=0&&NULL<=10);
	}
	~new_progress_timer(){

		try{
			istream::fmtflags old_flags=m_os.setf(istream::fixed,istream::floatfield);
			streamsize old_prec=m_os.precision(N);

			//输出时间
			m_os<<elapsed()<<"s\n"<<endl;

			//恢复流的状态
			m_os.flags(old_flags);
			m_os.precision(old_prec);
		}catch(...){
			//do nothing
		}
	}
private: 
	ostream &m_os;
};

int _tmain(int argc, _TCHAR* argv[])
{	
	new_progress_timer<10> t;

	//cout<<t.elapsed(); 这里不需要亲自调用，当超过t的作用域的时候自动调用
	return 0;
}