[Caml-list] Writing preprocessor using compiler-libs

[Caml-list] Writing preprocessor using compiler-libs

[Christophe Raffalli]

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Hello,

There are a few examples and documentation on how to write syntax extensions without camlp4 using -ppx compiler flags.

However, I could not find an example of writing a preprocessor compatible with -pp only using compiler-libs and without camlp4 ?

Anyone with an example, even very simple like a calculator ;-) Or some guide lines ...

Cheers,
Christophe

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Re: [Caml-list] Writing preprocessor using compiler-libs

[Peter Zotov]

On 2014-07-30 01:47, Christophe Raffalli wrote:
> Hello,
> 
> There are a few examples and documentation on how to write syntax
> extensions without camlp4 using -ppx compiler flags.
> 
> However, I could not find an example of writing a preprocessor
> compatible with -pp only using compiler-libs and without camlp4 ?

The input format for -pp is plaintext; you can trivially use Lexer
and Parser from compiler-libs to get an OCaml AST.

The output format for -pp is either plaintext ('-pp cat' works), in
which case you can use Printast or Pprintast; or the same as for -ppx,
distinguished by the magic number, in which case you may use the
code from Ast_mapper[1] as an example.

   [1]: 
https://github.com/ocaml/ocaml/blob/68fe1ebd5a33636afd075419fa0362741f33f878/parsing/ast_mapper.ml#L652-L656

-- 
Peter Zotov