Is it possible the get the AST for an OCaml program?

I'd like to be able to get the AST for a given OCaml program (I'd like to walk the AST and generate an instrumented version开发者_JS百科 of the code or do some kind of transformation, for example). Do any of the OCaml tools support this functionality?

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Since OCaml 4.02.1 it is possible to use the PPX tools written bu Alain Frisch to precisely do this. Example:

% ocamlfind ppx_tools/dumpast -e "1 + 2"
1 + 2
==>
{pexp_desc =
  Pexp_apply ({pexp_desc = Pexp_ident {txt = Lident "+"}},
   [("", {pexp_desc = Pexp_constant (Const_int 1)});
    ("", {pexp_desc = Pexp_constant (Const_int 2)})])}
=========

It is possible to use this program to dump the AST of a normal code file as well, and various options control the degree of precision of the dump. In the example above, for instance, the location parameters of the AST are hidden.

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camlp4 is a way to go. Here is a motivating example. The docs are sparse - true, but one can make his way reading through wiki, existing examples, tutorials, and maybe even camlp4 sources.

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What you're looking for is [camlp4][1]. I haven't used camlp4 before, so I can't attest to it's virtues as software. I have heard of people using camlp5 [http://pauillac.inria.fr/~ddr/camlp5/] which, according to wikipedia, has better documentation than the current version of camlp4.

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You can use compiler-libs to achieve this. See Parsetree, Asttypes, and Ast_helper.