title: type error with CamlinternalFormatBasics.fmt
body: <p>I am writing loop by recursion and I have problem: </p>
  
  <pre><code>let isRectangleIn a b c d =
    if (a &gt; c &amp;&amp; b &gt; d) || (a&gt;d &amp;&amp; b&gt;c) 
      then 
        "TAK"
      else
        "NIE";;
  
  let rec loop k =
    if k = 0 then 0 else 
    let a = read_int () in
      let b = read_int () in
        let c = read_int () in
          let d = read_int () in
              Printf.printf "%s \n" (isRectangleIn a b c d)
              loop (k-1);;
  
  
  let i = read_int ();;
  let result = loop i;;
  </code></pre>
  
  <p>Compiler says that</p>
  
  <pre><code>This expression has type
           ('a -&gt; 'b -&gt; 'c, out_channel, unit, unit, unit, 'a -&gt; 'b -&gt; 'c)
           CamlinternalFormatBasics.fmt
         but an expression was expected of type
           ('a -&gt; 'b -&gt; 'c, out_channel, unit, unit, unit, unit)
           CamlinternalFormatBasics.fmt
         Type 'a -&gt; 'b -&gt; 'c is not compatible with type unit 
  </code></pre>
  
  <p>but I dont understand what i am doing wrong. Can somebody help me?</p>