Re: [Caml-list] [ANN] visitors

[whitequark <whitequark@whitequark.org>]

On 2017-01-30 16:04, François Pottier wrote:
>> A big difference is that it load type definition from .cmi files 
>> directly.
> 
> Indeed, a limitation of the ppx approach is that it is purely syntatic:
> a syntax tree (the type definition) is turned into a syntax tree (the
> definition of the visitor classes). In particular, at the moment, 
> "visitors"
> cannot generate visitor classes for a pre-existing type. Perhaps one 
> could
> write a tool that reads a .cmi file, but I suppose it would have to be
> explicitly invoked as an external tool. I will think about it.

I wrote this tool long ago, it's called ppx_import[1]. In fact it 
motivated
some improvements to the compiler, chiefly the way to extract the set of 
-I paths.
It's even linked from ppx_deriving README[2].

[1]: https://github.com/whitequark/ppx_import
[2]: 
https://github.com/whitequark/ppx_deriving/#working-with-existing-types

-- 
whitequark