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Message-ID: <6cb897b30712140855m4c14ef70v73ebc1616ece8e69@mail.gmail.com>
Date: Fri, 14 Dec 2007 17:55:50 +0100
From: "Pierre-Evariste Dagand" <pedagand@gmail.com>
To: "Zheng Li" <li@pps.jussieu.fr>, caml-list@yquem.inria.fr
Subject: Re: [Caml-list] Re: "Ref" and copy of functions
In-Reply-To: <87zlwdi7cf.fsf@pps.jussieu.fr>
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References: <6cb897b30712130927m7df88e3axec56eacba4d47fdf@mail.gmail.com>
	 <87d4t9k0uy.fsf@pps.jussieu.fr>
	 <6cb897b30712140654v26a0ef96we6007c868d3d1829@mail.gmail.com>
	 <87zlwdi7cf.fsf@pps.jussieu.fr>
X-Spam: no; 0.00; mutation:01 ad-hoc:01 high-level:01 mutable:01 ocaml:01 existential:01 encode:01 caml-list:01 caml-list:01 functions:01 marshal:01 closure:01 closure:01 functional:02 cps:02 

> I guess you won't be able to find such a solution. In the Ref-based
> implementation, the result arrow type is stateful. You won't be able to
> _implicitly_ copy a state _inside_ the language, otherwise first-class
> continuation would already appear.

That's why I asked this to the Caml-list : to find a black magic recipe :-)

> Since the corresponding mechanics in Ref and CPS are mutation and
> closure (de)construction, no wonder the former is faster. One ad-hoc
> solution, if you only have to provide high-level functional API to
> outside, is to make states explicit, like
>
> type ('a,'b) arrow = {mutable state: 'c; eval: 'c -> 'a -> 'b}
>
> This is not valid OCaml, since the 'c type is out of scope. You can
> either encode it with existential type (which also involve closure
> (de)construction, but I'm not sure about the cost). Or simply using
> Obj.t instead of 'c as far as you won't expose it, at least it won't be
> unsafer than Marshal and faster.

This solution looks promising, I will look at it and see if it suits my needs.

Thanks,

-- 
Pierre-Evariste DAGAND