Re: [Caml-list] [ANN] ppx_deriving 3.0

[Yaron Minsky <yminsky@janestreet.com>]

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Jeremie just air-dropped about 25k lines of PPX code on github and opam, so
OCaml's PPX tools are finally out there.  You can find them here:

https://github.com/janestreet

On Fri, Sep 25, 2015 at 5:00 PM, whitequark <whitequark@whitequark.org>
wrote:

> Hello,
>
> I am glad to announce ppx_deriving 3.0. It brings two
> major changes: hygiene and ppx_type_conv compatibility.
> It is installable via opam[1].
>
> First, hygiene. Earlier versions of ppx_deriving:
>   1) assumed that all the modules that the deriver
>      requires are not shadowed with a different signature;
>   2) included user-specified code such as from [@default]
>      attributes in a way that exposed deriver-internal
>      identifiers to such code.
>
> Now, ppx_deriving includes a mechanism for hygienic
> unquoting[2], as well as a module[3] containing references
> to most standard library modules under their proper names.
> This allows it to coexist with e.g. `open Core.Std`.
>
> Second, ppx_type_conv compatibility. You probably don't
> know it yet, but Jane Street has converted all their syntax
> extensions to ppx, so now there's ppx_type_conv, ppx_sexp_conv,
> etc. I've coordinated the development of ppx_deriving with
> Jane Street, so now ppx_deriving and ppx_type_conv use
> the same syntactic conventions. In fact, they share
> the [@@deriving] syntax without any effort from the user!
>
> Furthermore, I have been looking at the sources of Jane Street's
> ppx_core, ppx_driver, ppx_type_conv, etc and I find these
> projects exceptionally well designed; further, they tackle some
> important problems that ppx_deriving has explicitly left out of
> scope, such as attribute hygiene.
>
> While these libraries have a somewhat larger API, I think anyone
> writing a new deriver should consider using ppx_type_conv.
> I cannot outright recommend that since I have not actually
> tried it (yet?), but it sounds worthwhile.
>
> [1]: http://opam.ocaml.org/packages/ppx_deriving/ppx_deriving.3.0/
> [2]: https://whitequark.github.io/ppx_deriving/Ppx_deriving.html#2_Hygiene
> [3]: https://whitequark.github.io/ppx_deriving/Ppx_deriving_runtime.html
>
> --
> whitequark
>
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