Fa3ien  wrote in message <4707ba6b$1@news.povray.org>:
> With built-in functions, i can write :
> light_source {... area_light ... circular orient adaptive 2}
> or, as well
> light_source {... area_light ... adaptive 2 orient circular}
> 
> I know that almost no programming language allows that kind
> of parsing feature in user-defined functions, but I regret it.

If you do not mind naming all the parameters, a lot of languages can do
that.

Objective Caml can do something like that:

light_source ... ~area_light:true ~shape:`Circular ~adaptative:2 ()

Python has a similar feature, I think.

Perl can emulate that very well using hashes:

light_source ... area_light => 1, shape => "circular", adaptative => 2;

And in fact, almost any language that supports variable number of arguments
can emulate it. For example in C:

light_source(..., "area_light", "circular", "orient", "adaptative", 2, NULL);

This requires a little bit more work inside the user-defined function, but
not much, and some of it can be eased by common helper functions.

Some libraries, like Gtk+, use similar schemes.

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