# \#visitors

**URL:** https://discuss.ocaml.org/tag/visitors/33.md

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## [Ppx\_deriving: opaque for visitors but not for show](https://discuss.ocaml.org/t/ppx-deriving-opaque-for-visitors-but-not-for-show/3577)

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**Author:** [@thierry-martinez](https://discuss.ocaml.org/u/thierry-martinez)\
**Replies:** 2\
**Last updated:** [March 27, 2019, 10:40pm UTC](https://discuss.ocaml.org/t/ppx-deriving-opaque-for-visitors-but-not-for-show/3577 "2019-03-27T22:40:28Z")

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I use ppx\_deriving both for deriving printers (show) and visitors (https://gitlab.inria.fr/fpottier/visitors). Both derivers recognize the \[@opaque\] annotation to ignore some branches of the type. I would like to declar…

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## [Issue with preprocessing with \`visitors\`](https://discuss.ocaml.org/t/issue-with-preprocessing-with-visitors/331)

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**Author:** [@grayswandyr](https://discuss.ocaml.org/u/grayswandyr)\
**Replies:** 0\
**Last updated:** [June 2, 2017, 9:05am UTC](https://discuss.ocaml.org/t/issue-with-preprocessing-with-visitors/331 "2017-06-02T09:05:10Z")

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Hi, anyone knows how to configure the jbuild file to use F. Pottier’s “visitors” PPX? EDIT: oh right it seems that jbuilder only works with package relying on ocaml-migrate-parsetree, which does not seem to be the case …