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Subject: [Caml-list] how (within camlp4 printer) can I traverse AST ?

Hello,

I would like to write a (camlp4 pluggable) printer.

My starting-point is this:

http://brion.inria.fr/gallium/index.php/Setup_a_new_printer

It was easy to figure out that "ast" arguments have type "Ast.sig_item"
or "Ast.str_item" respectively which are both abstract types
http://camlunity.ru/doc/camlp4-3.12/Camlp4.Sig.Ast.html
so I cannot try to match them---I cannot use any of the constructors
defined in:

http://camlunity.ru/doc/camlp4-3.12/Camlp4.Sig.Camlp4Ast.html

What is thus a proper way of traversing ASTs?