Module Pa_lwt

module Pa_lwt: sig .. end

Syntactic sugars for lwt

---

This extension add the following sugars:

• anonymous bind:

         put_string stdio "Hello, " >>         put_string stdio "world!" >>         x := 1;         sleep 1.0 >>         return 1      

• lwt-binding:

         lwt ch = get_char stdin in         code      

is the same as bind (get_char stdin) (fun ch -> code)

Moreover it supports parallel binding:

         lwt x = do_something1 ()         and y = do_something2 in         code      

will let do_something1 () and do_something2 () runs then bind their result to x and y. It is the same as:

         let t1 = do_something1         and t2 = do_something2 in         bind t1 (fun x -> bind t2 (fun y -> code))      

• exception catching:

         try_lwt           <expr>      

,

         try_lwt           <expr>         with           <branches>      

,

         try_lwt           <expr>         finally           <expr>       

and:

         try_lwt           <expr>         with           <branches>         finally           <expr>      

For example:

         try_lwt           f x         with           | Failure msg ->               prerr_endline msg;               return ()      

is expanded to:

         catch (fun _ -> f x)           (function              | Failure msg ->                  prerr_endline msg;                  return ()              | exn ->                  Lwt.fail exn)      

Note that the exn -> Lwt.fail exn branch is automatically addedd when needed.

The construction try_lwt <expr> just catch regular exception into lwt exception. i.e. it is the same as catch (fun _ -> <expr>) fail.

• for loop:

        for_lwt i = <expr> to <expr> do          <expr>        done      

and:

        for_lwt i = <expr> downto <expr> do          <expr>        done      

• iteration over streams:

        for_lwt <patt> in <expr> do          <expr>        done