Warp wrote:
> Fa3ien <fab### [at] yourshoesskynetbe> wrote:
>> POV-Ray allows you to do that, not as a side-effect of the SDL, but
>> precisely BY DESIGN.  Drop that, and you kill POV-Ray (there are
>> already many nice and free pure renderers out there).
> 
> Thus all you who are worrying about the "new SDL" being some cryptic
> high-end programming language only a few can understand, you have got
> it completely wrong: Keeping the current ease-of-use and, as far as
> possible, the same syntax, is a *major* concern in the designing of
> the new SDL. You don't have to express your concern about this.
> 
>   (Of course a different issue is whether there's enough manpower and
> expertise to actually develop and implement such a language.)
> 

When I have a few minutes here and there, I'm working on a technique 
which retains the current SDL (with the possible exception of macros as 
they currently exist) but makes it user-expandable.  The POV SDL syntax 
doesn't need to be the huge complex thing that it appears to be.  For 
example, consider the following snippet of SDL:

camera {
    location <-5, 10, -15>
    direction <0, 0,  2.25>
    right x*1.33
    look_at <0,0,0>
}

sky_sphere {
     pigment {
         gradient y
         color_map {
             [0, 1  color Gray50 color Gray80]
         }
     }
}

The parts of the syntax would include things like 1.33, <-5, 10, -15>, 
{} and []. The rest of the identifiers name methods written in either 
the SDL itself or a high level programming language.

The semantics would be something like:

camera
	- call the camera method to:
		- create an instance of a camera
		- add it to the scene
{
	- push it on the stack

location
	- call the location method to:
		- expect a vector parameter to follow
		- apply to the top of stack (the camera)

}
	- pop the stack


sky_sphere
	- call the sky_sphere method to:
		- create a sky_sphere
		- add it to the scene
{
	- push it on the stack

pigment
	- call the pigment method to:
		- create a new pigment
		- apply it to the sky sphere
{
	- push the pigment on the stack

etc...

The words like camera, location, pigment, and so forth are no longer 
part of the syntax - they are methods that are called by the parser.  To 
add new functionality, you can add new methods which can be written in 
either SDL or the high level programming language.

It seems to me like the whole SDL grammar can be modelled this way which 
would give backwards compatibility as well as expandability.


Thoughts?

David Buck

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