[Caml-list] Re: working %.pp.ml target with ocamfind/ocamlbuild

[Hongbo Zhang <bobzhang1988@gmail.com>]

Greetings,
On 9/9/12 6:29 PM, Wojciech Meyer wrote:
> Gabriel Scherer <gabriel.scherer@gmail.com> writes:
>
>> This is useful for debugging purposes, and for some (minor) modes of
>> use of Camlp4. However, for most Camlp4 development, this has the
>> severe downside of losing the location information of the original
>> file, if I understand correctly. This means that you don't want to use
>> it as a transparent step towards compilation, but only in exceptional
>> situations where the developers will re-edit the output code.
>
> I think I've to say I disagree it's not useful, when I'm developing a
> syntax extension on top of Camlp4 I really want to see the generated
> code. Moreover to understand some of the more complicated syntax
> extensions like type_conv, deriving, FoldGenerator I need to look at the
> expanded code to understand how to use it - last time I hit the same
Yes, it's damn useful not only for bootstrapping, but also for 
developing to locate type errors. But there's something wrong with 
Camlp4's printer, it has *4* printers in total, writing a printer for an 
Ast which has no backend is totally useless. In my branch of camlp4, *I 
removed all those 4 printers and using tools/pprintast.ml* in ocaml's 
compiler source tree(with some my own bug fixes), and it works very well.
Btw, are you in ICFP? we could have a talk about Camlp4 :-)
> problem it was actually 'deriving-ocsigen' when I needed to implement my
> own Show module - it's just much faster to see what's being generated
> for the usual case, then trying to figure out from the recipe in the
> documentation.  Otherwise for bootstrapping purposes, you might want to
> pre-generate some code too and put into the repository.
>
> --
> Wojciech Meyer
> http://danmey.org
>