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[Camlp4] Quotation expander with OCaml syntax
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Date: -- (:)
From: Thomas.Gazagnaire@s...
Subject: Re: [Caml-list] [Camlp4] Quotation expander with OCaml syntax
Are you trying to the same thing as HOP [1] ?

What kind of restrictions do you impose on the expressions you can
transfer from the server to the client (only non-functional values) ? How
do you ensure them in your program ?

Are you sure splitting the code into two parts is sufficient ? How will
you handle branching than you can decide only at runtime, as example ? HOP
is using a javascrip compiler embedded in a library to compile efficiently
the right client code at runtime.

Btw, would be glad to have more details on what you have done and plan to
do as I am working on similar things (not very actively currently) : I've
been trying  to make camloo, a caml-light to bigloo compiler, working
again (current version[2] is quite working - still few things to finish).
At one point, the goal would be to extand the source language with similar
constructs than yours  and to compile to HOP ...

[1] http://hop.inria.fr
[2] http://www-sop.inria.fr/members/Thomas.Gazagnaire/
--
Thomas

> Hi all,
>
> I'm working on a syntax extension as part of an internship in the
Ocsigen team. The aim of the syntax extension is to split the code of a
web
> application in two separate files: one for the client and one for the
server. A
> few transformations are to take place in the process.
>
> Quotations are to be transformed into client code while antiquotations
can
> refer
> to server side values transmitted to the client at runtime.
>
>
> In order to avoid any XY problems, here is an abstracted and simplified
example
> of the expected behavior:
>
> (* Pre-parsed code: *)
> let start = <:on< f $y$ >> in
> let html_node =
>  span ~a:[onclick start] "some text" (* a is used for (html) attributes
*)
>
> (* Server side post-parsed code: *)
> let start _arg1 =
>  "call_closure(some_unique_name," ^ mymarshall _arg1 ")"
> in
> let html_node = span ~a:[onclick (start y)] "some text"
>
> (* Client side post-parsed code: *)
> let _ = register_closure some_unique_name (fun _arg1 -> f _arg1)
>
>
>
> If the example isn't clear enough I can detail it a little bit more.
>
>
> I'm unsure of what is the standard way of doing such a thing in Camlp4.
What
> I
> have in mind is to use the original Ocaml syntax for the quotation
expander.
> This would (IIUC) allow me to filter the AST to transform every
> antiquotation
> found inside the quotation itself.
>
> I'm not sure this is the ideal way of doing such a thing because of the
size
> of
> the pattern matching in the AST filter. On the other hand, because the
quotation
> is supposed to contain valid OCaml code, it seems normal to reuse the
original
> parser.
>
> I considered an alternative solution: treating quotations as raw text (with
> a
> custom quotation expander) but that would destroy any _loc information
and
> make
> compile time warnings and errors quite difficult to locate.
>
>
> Is there a simpler/fitter way of doing that? (Is the Y correct wrt the
X?)
>
> How can one embed the original parser in a quotation expander? (I
couldn't
> find
> a function of type string -> Ast.expr in the Camlp4 doc/mlis, but I'd be
happy
> to be pointed to one if it exists. I think it would at least require
some
> functor application.)
>
> Does anyone know of any example that resemble what I'm trying to
achieve?
>
>
>
> --
> _______
> Raphael
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