thanks a lot for this information and the links, this is very helpful

On Thu, Sep 23, 2010 at 6:26 PM, Michael Ekstrand <michael@elehack.net> wrote:
> On Thu, 2010-09-23 at 16:56 +0200, ben kuin wrote:
>> Could someone give any idea how I can begin to understand how to write
>> simple camlp4 extensions?
>
> Shameless self-plug, but I wrote a blog post this summer about my
> experience figuring out how to do it.  I provide a walk-through and
> explanation of a minimal syntax extension which adds lazy list pattern
> matching support based on Batteries.  The URL:
>
> http://www.elehack.net/michael/blog/2010/06/ocaml-syntax-extension
>
> I do assume a basic knowledge of parsing context-free grammars, but a
> generic tutorial on parsing with a tool such as Yacc can fill in that
> gap.  The Wikipedia article[1] may also be helpful.
>
> Once you've lept the hurdle of figuring out what pieces you need to
> write and build a syntax extension, the remaining tricky part is to
> figure out what pieces of the grammar you need to extend to accomplish
> your objective.  For that, I consult the definition of the OCaml parser
> in Camlp4OCamlParser.ml in the OCaml source tree.
>
> - Michael
>
> 1. http://en.wikipedia.org/wiki/Context-free_grammar
>
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>