C++ :: Writing A Vector To Specified File - Getting Semantic Error

I have written a function that is supposed to write a vector to a specified file. When I build the solution, I get this error:

- Semantic error. Invalid operands to binary expression.

This is the code for the function.

void file_out(vector<task>Task, string myfilename){
//writing vector to file
string file_out = myfilename;
ofstream output_file(file_out);
ostream_iterator<task> output_iterator(output_file, "
");
copy(Task.begin(), Task.end(), output_iterator);
};