c++ - 为什么我在构造它时不能传递 ifstream？

Question

编译器不喜欢下面的主程序

int get1(ifstream &f){
  int count;
  f >> count;
return count;
}

int main(int argc, char** argv){
  cout << get1(ifstream(argv[1])) << endl;
}

错误信息是：

test.cpp: In function 'int main(int, char**)':
test.cpp:11:33: error: invalid initialization of non-const reference of type 's\
td::ifstream& {aka std::basic_ifstream<char>&}' from an rvalue of type 'std::if\
stream {aka std::basic_ifstream<char>}'
test.cpp:4:5: error: in passing argument 1 of 'int get1(std::ifstream&)'

如果主程序写为

int main(int argc, char** argv){
  ifstream f(argv[1]);
  cout << get1(f) << endl;
}

有没有办法使紧凑的第一种形式起作用？

Answer 1