Beta Gen Documentation

Hi Wesley,

Jumping the gun a bit, but will there be an SDK for [gen~] operators at any point? That would really be the icing on the cake.

An SDK is something we are hoping for a future release (no promises although I really want to see it too). I will say it won't be in a 6.0 release though.

Excellent document - like many others I am very enthusiastic about gen and its Jitter cousins. A few questions:

- GenExpr language: in the case of only being interested in one return value from an expression, the document describes the case where you assign the first return value to a variable but discard the second. Is there a way to reverse this - to discard the first return value and assign the second?

- is the namespace in codebox global - i.e. if I define a function in one codebox can it be called in another?

- is it possible to add the equivalent of the history operator in a jit.gen or (more importantly) jit.gl.gen context? This would be an extremely elegant way to allow for feedback processes, but I don't know if it's feasible. As FBO's are not readable in GLSL I'd imagine the answer is no, but worth asking.

"- GenExpr language: in the case of only being interested in one return value from an expression, the document describes the case where you assign the first return value to a variable but discard the second. Is there a way to reverse this - to discard the first return value and assign the second?"

// the Gen compiler does dead code elimination, so the variable "notused" won't actually be used
notused, myvar = cartopol(in1, in2);
out1 = myvar;

"- is the namespace in codebox global - i.e. if I define a function in one codebox can it be called in another?"

not currently. We will support some kind of import message in the near near future that will load in files of
function definitions

"- is it possible to add the equivalent of the history operator in a jit.gen or (more importantly) jit.gl.gen context? This would be an extremely elegant way to allow for feedback processes, but I don't know if it's feasible. As FBO's are not readable in GLSL I'd imagine the answer is no, but worth asking."

No. None of the Gen objects support this operator. As you can imagine, for the history operator, we'd have to create a temporary buffer the size of the input matrix for this to work. While technically feasible in jit.gen and jit.pix, it's not at all possible in jit.gl.pix. Since the jitter Gen objects don't suffer from the "single sample" delay problem that MSP objects do in feedback situations, I don't think it's much of a burden to require feedback jitter Gen patchers require the user to loop the output back to a second input.

> Here's the link:
> https://cycling74.com/download/gen.documentation.beta.pdf

Most pictures in the first pages of the document are incorrectly displayed in Adobe Reader (8.1.1) (but are OK in MacOS X's Preview app).

Thanks Wesley - all confirming what I had guessed. It's good to hear that you will support function import at some point in the future.

Thanks Roald. I'm seeing the same in Acrobat Pro. Really odd! Looks like the print to PDF function munged some things up.

Really useful document, thanks! I've been muddling along with gen~ for the last few days but this makes things much clearer.

A small question - is it possible to use the history operator within a codebox? It currently throws up an error, so I'm guessing it's not allowed. That's a shame if so. It'd be a great way to easily implement more unwieldy filters.

Hi Bacchus,
In the beta, we didn't get to implementing History in a codebox, but for the release this is already in there. The syntax will like this:

y = x + 1; // fwd use of x
x = history(y * 2);
out = y;

note that x is used before it's assigned to. This will _only_ be allowed for feedback operations and we enforce that strictly. Anything else will throw errors.