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[Caml-list] Even at compile time 2*2=4!
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Date: -- (:)
From: Daniel de Rauglaudre <daniel.de_rauglaudre@i...>
Subject: Re: [Caml-list] Even at compile time 2*2=4!
Hi,

On Mon, Nov 18, 2002 at 07:18:34PM -0800, Jakob Lichtenberg wrote:

> 2. Can I build a new top-level interactive environment 'ocaml_with_fourLib'
> where this module is 'pre-loaded'.  Again, the actual calculation of 2*2
> should be done when I build ocaml_with_fourLib - not when I start it.

There is no difference between "load" a module and "start" it: the fact
of loading it is starting it.

In some cases, you could resolve your problem with Camlp4, if your
computation can be done at parse time. We can imagine a syntax
extension, e.g. "compute" followed by an expression, ask the
preprocessor to evalutate it and build the syntax tree of the
result. For example:
    compute (2*2)
would generate at parse time:
    4

But this could not work:
    let x = 2 in
    compute(x*x)
because the preprocessor does not know what is "x".

On the other hand, if "x" is defined as a directive to the preprocessor,
for example with "DEFINE x = 2" (new syntax extension pa_macro.cmo), it
could work.

-- 
Daniel de RAUGLAUDRE
http://cristal.inria.fr/~ddr/
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