C++ "hello world" Boost tee example program
我们的目标是:
auto myTeeStream = make_tee(std::cout, myfile);
在尝试用函数make\u tee包装这个用法以允许参数的自动类型推断之后,我意识到copy和move构造函数对于必要的类型都不可用。
所以:
在c++11中有没有一种合理的方法来包装tee流的创建
以下是由于删除了复制构造函数和缺少移动构造函数而导致编译失败的尝试:
#include <iostream>
#include <ostream>
#include <fstream>
#include <boost/iostreams/tee.hpp>
#include <boost/iostreams/stream.hpp>
template <typename StreamT1, typename StreamT2>
boost::iostreams::stream<boost::iostreams::tee_device<StreamT1, StreamT2> >
make_tee(StreamT1 & t1, StreamT2 & t2)
{
using boost::iostreams::stream;
using boost::iostreams::tee;
return stream<decltype(tee(t1,t2))>(tee(t1,t2)); // compile error
//return std::move(stream<decltype(tee(t1,t2))>(tee(t1,t2))); // also fails of course
}
int main()
{
{
// desired usage
std::ofstream myFile("file.txt");
auto && myTee = make_tee(std::cout, myFile); // required from here
}
{
// noisy default usage
std::ofstream myFile("file.txt");
using boost::iostreams::tee;
using boost::iostreams::stream;
auto && myTee = stream<decltype(tee(std::cout, myFile))>(tee(std::cout, myFile));
}
return 0;
}
clang++ --std=c++11 teetest.cpp
是:
teetest.cpp:14:12: error: call to implicitly-deleted copy constructor of 'boost::iostreams::stream<boost::iostreams::tee_device<basic_ostream<char>, basic_ofstream<char> > >'
