Module Pa_lwt
module Pa_lwt: sig..end
Syntactic sugars for lwt
This extension add the following sugars:
- anonymous bind:
write stdio "Hello, " >> write stdio "world!"
- 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