关于 istream_iterator的错误

街头霸王爷

f()
{
typedef set<string>::difference_type diff_type;
.........
istream_iterator<string,diff_type> input_set(infile),eos; //这里出现了编译错误
copy(input_set,eos,inserter(exclusion_set,exclusion_set.begin()));
........
}
错误信息：
D:\programe\C++ primer\test2\main.cpp(229) : error C2664: '__thiscall std::istream_iterator<class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,int,struct std::char_traits<int> >::std::istream_iterator<class std::
basic_string<char,struct std::char_traits<char>,class std::allocator<char> >,int,struct std::char_traits<int> >(class std::basic_istream<int,struct std::char_traits<int> > &)' : cannot convert parameter 1 from 'class std::basic_ifstream<char,struct
std::char_traits<char> >' to 'class std::basic_istream<int,struct std::char_traits<int> > &'
A reference that is not to 'const' cannot be bound to a non-lvalue

怎么解决这个错误，谢谢：）