example/h-sql: document Lwt.bind

example/h-sql/README.md

@@ -17,8 +17,7 @@ let list_comments =
     (T.unit ->* T.(tup2 int string))
     "SELECT id, text FROM comment" in
   fun (module Db : DB) ->
-    let%lwt comments_or_error = Db.collect_list query () in
-    Caqti_lwt.or_fail comments_or_error
+    Lwt.bind (Db.collect_list query ()) Caqti_lwt.or_fail
 
 let add_comment =
   let query =
@@ -79,6 +78,9 @@ comments!
 
 <br>
 
+Note that the `let%lwt` syntax is syntactic sugar for `Lwt.bind`, so the two forms above are equivalent (a third option would be using `>>=`). For more information, see [here](https://ocsigen.org/lwt/latest/api/Lwt#3_Callbacks).
+
+
 We take the opportunity to try out
 [`Dream.sql_sessions`](https://aantron.github.io/dream/#val-sql_sessions), which
 stores session data persistently in `db.sqlite`. See example