title: How to fix Ocaml Unbound constructor error
body: <p>I am brand new to OCaml. I am trying to write this basic recursive function called H sequence. Here is my code:</p>
  
  <pre><code>let rec H n = 
      if n == 0 then
          0
      else 
         n - H(H(H(n - 1)))
  ;;
  
  
  print_int(H 3);
  
  </code></pre>
  
  <p>I am pretty sure my function H is correct However I get this error:</p>
  
  <pre><code>File "main.ml", line 1, characters 8-9:
  Error: Unbound constructor H
  </code></pre>
  
  <p>I am not sure how and what to bind to H. If anyone can give me some advice it would be much appreciated. If it helps I am using this website to run my code: 
  <a href="https://www.tutorialspoint.com/compile_ocaml_online.php" rel="nofollow noreferrer">https://www.tutorialspoint.com/compile_ocaml_online.php</a> </p>