-<pre>
-# let ( * ) m f = match m with None -> None | Some n -> f n;;
-val ( * ) : 'a option -> ('a -> 'b option) -> 'b option = <fun>
-# let unit x = Some x;;
-val unit : 'a -> 'a option = <fun>
-# unit 2 * unit;;
-- : int option = Some 2
-</pre>
+ <pre>
+ # let ( * ) m f = match m with None -> None | Some n -> f n;;
+ val ( * ) : 'a option -> ('a -> 'b option) -> 'b option = <fun>
+ # let unit x = Some x;;
+ val unit : 'a -> 'a option = <fun>
+ # unit 2 * unit;;
+ - : int option = Some 2
+ </pre>