package ppx_defer
Go-like [%defer later]; now syntax
Install
Dune Dependency
Authors
Maintainers
Sources
ppx_defer-v0.5.0.tbz
sha256=802092d24925eb163663567c7c1d0bdf1e9d0a7e6a58b0854b78fa24a19df05c
sha512=dabf65b2674a6780677bfb56c501992a4f495c41343e47f2bab57fe533f06f68adca0d9d48df4b26b7391cf5fee544498c2641653ddbc401f2f76c28e0b951a9
Description
Published: 10 Sep 2021
README
ppx_defer - Go-like [%defer later]; now
syntax.
This is an OCaml language extension implementing a somewhat Go-ish [%defer expr1]; expr2
which will defer the evaluation of expr1
until after expr2
. expr1
will still be evaluated if expr2
raises an exception.
If you are using Lwt you can use [%defer.lwt expr1]; expr2
.
Thanks to Drup for guidance in figuring out ppx details!
Using ppx_defer
As a simple example this code
let () =
[%defer print_endline "world"];
print_endline "Hello"
will print
Hello
world
as print_endline "world"
was deferred until after print_endline "Hello"
.
A more common use case would be closing an external resource at the end of the current expression.
let () =
let ic = open_in_bin "some_file" in
[%defer close_in ic];
let length = in_channel_length ic in
let bytes = really_input_string ic length in
print_endline bytes
This will close_in ic
at the end of the current expression, even if an exception is raised.
See the examples/
directory for more examples.
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>
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