title: How to output a list of strings into a file with printf
body: <p>I aim to write a function to read a string list <code>persons</code> with <code>open_out</code> and store it in the file <code>filename</code>
  I tried to iterate over it with List.fold_left and use <code>printf</code>, however it is not working.</p>
  <pre><code>let write_list filename persons =
    let file = open_out filename in 
    let write_person p =
      let rec ite_pres aux acc = List.fold_left (Printf.fprintf file &quot;%s\n&quot; filename )
      List.iter write_person persons;
    close_out 
  </code></pre>