Passing control methods into functions how?

[witt0191]

Hi been looking at this all day and just cant get it to work

Trying to spork a function with what I think is called a control method as an argument eg.

[Kassen]

Yes, I see.

In ChucK functions aren't objects and so can't be used as parameters. What you can do though is pass a object like a UGen as a parameter, then call a member function on that.

if you really, absolutely, must use references to functions you will have to create a "functor" class with a single member function called something like "do()" that you would overload for various such functions. You'd then pass a instance of one of those classes and call the ".do()" on that reference.

How you'd go about this depends a bit on what you'd like to accomplish.

[witt0191]

[Antimon]

Curious how function-oriented programming is seeping into the mainstream (not assuming you're mainstream, witt0191, I just see this stuff more and more everywhere). I feel like I'll be old hat soon with my object-oriented thinking (not to mention that I lapse into procedural programming every now and then), if I don't read up on this stuff.

Something like this maybe:

[Kassen]

Here you go;

[Kassen]

[witt0191]

Hi,

Thanks for your replies.

I find that I tend to write functions and then spork them to change values like in the example above often, so I though that being able to throw the direct target into them rather than creating one for each purpose would be useful. Also could imagine use in a more dynamic system for that sort of capability.

Could see myself wanting to do something like

spork ~ changevalue(s.freq);
spork ~ changevalue(k.freq);

I suppose to be really useful there would be additional arguments setting other variables in the function

spork ~ changevalue(s.freq,500,1000::ms);

I could see this allowing me to reuse lots of functions more

[Kassen]

Yes, but in that case it's different, in that case you pass the UGen (which is already a object) as the argument.

[witt0191]

Hi,

Thats ace could just explain whats going on in this portion of your code?

(u $ SinOsc)

thanks really like that

[Antimon]

[Kassen]

Indeed.

more formally; things like SinOsc, LPF and Moog are all UGens and all have a .freq() member function. However, the "UGen" object iself doesn't have one and is just a abstraction (in fact it's virtually indentical to "Gain").

So; if we have a function that we'd like to be able to pass all of those types of UGens it would need to take "Ugen" as it's argument type.

Now there is a issue, as we may have a SinOsc (that does have a .freq) but we are considering it like a UGen, making the .freq inaccessible.

Here the cast ($) operator comes in. We can cast any type to a type that extends it (also to a type it's a extension off and float and int can be cast to each other). So; we cast this UGent-argument to a type that we know has the desired member function.

WARNING; this work, it's legal... but we are over-riding the type system so the type system no longer helps us make sure we are not making typos. When you would feed a "Gain" to this function you will have a VM crash. In the case of the mini that will mean losing all your unsaved code.

It's more or less like when I'd hand you a box and say there is a animal in it. You would not say say "I'm going to milk it" on your own because not all animals can be milked; there might be a beetle in there. The casting is like me guaranteeing you there is a cow, sheep or snake in there (that you will have to milk). If I'd make a mistake and accidentally put a ostrich in the box you would probably quit following my orders as they make no sense, which is exactly what the VM will do.

[blue hell]

Does ChucK have run time type information? Such that I could ask an UGen if it in fact is an osc, or if in fact does have a freq() method?

In Pascal I'd write something like :

if anObject is TOscillator
then TOscillator( anObject).frequency := 1000;

[Antimon]

Yeah, in Java you would type

[blue hell]