Hi ! I am starting to learn Beads audio library, wonderful book by Evan Merz but in Java.
The beads library works fine in Processing.py up to some points where the Java does not seem obvious to be translated in Python.
------> Has anybody tried to translate in Python the Merz book, or better the 11 Lessons ?
I am stuck with FM synthesis, having to translate a CUSTOM FUNCTION (much used in the book) :
modulator = new WavePlayer(ac, 5, Buffer.SINE);
// this is a custom function
// custom functions are a bit like custom Unit Generators (custom Beads)
// but they only override the calculate function
Function frequencyModulation = new Function(modulator)
{
public float calculate() {
// return x[0], which is the original value of the modulator signal (a sine wave)
// multiplied by 50 to make the sine vary between -50 and 50
// then add 200, so that it varies from 150 to 250
return (x[0] * 50.0) + 200.0; // <---- works fine !
}
};
carrier = new WavePlayer(ac, frequencyModulation, Buffer.SINE);
----------- I tried this but without luck :
class My_Function(Function) :
def calculate(self) :
return x[0]*50+200 # <---- x is not defined !!!
modulator = WavePlayer(ac,5,Buffer.SINE)
frequencyModulation = My_Function(modulator)
carrier = WavePlayer(ac,frequencyModulation,Buffer.SINE)
Any help ?
In your code editor (PDE, VS code, Eclipse, etc) ensure you execute the beautifier function. This function automatically indents your code. Auto-indenting makes your code easier to read and helps catching bugs due to mismatch parenthesis, for instance. In the PDE, you use the key combination: ctrl+t
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You don’t include headers, so I’m not sure – is Function imported from a standard Java library, or is it a custom method of Beads? To make a Python equivalent, first need to track down what exactly x is in the original Java and where it is coming from…
Can I?! Never used Python / Jython - have contributed to Beads! But if Jython can’t extend a Java class and access its protected members, it can’t really extend a Java class!
That would be kind to have a complete set of Beads Lessons in Python mode for those who do not program in Java (and your trick is a bit too clever as it requires Java knowledge of protected variables). Python Beads deserves more than the present number of users, notably for teaching, it’s a good job.
Thanks for the rest of us.
Jython treats any Java’s non-public members as if they were full-force private, regardless whether they have protected or “Package” more liberal access levels.
Although reflection techniques are “clever”, these 3 statements aren’t that hard to grasp IMO:
Believe me, if that field x[] were private instead of the less restrictive protected, the Java version would have a much bigger boilerplate for us to code:
import beads.*;
import java.lang.reflect.Field;
class FreqControl extends Function {
static final float MULT = 50.0, AUGMENT = 200.0;
final float[] xx;
@SafeVarargs FreqControl(final UGen... inputs) {
super(inputs);
try {
final Field fieldX = Function.class.getDeclaredField("x");
fieldX.setAccessible(true);
xx = (float[]) fieldX.get(this);
}
catch (final ReflectiveOperationException cause) {
throw new RuntimeException(cause);
}
}
@Override float calculate() {
return xx[0] * MULT + AUGMENT;
}
}
You should try convincing them to either change the field Function::x[] 's access level to public or include a public getter method for it:
Never used Beads library before; but you can always post your Java to Python Mode conversion attempts here in the forum.
I’ve merely listed the 2 possible easiest options to “fix” the issue for Processing’s Python Mode, regardless of their technical merit. Which 1 to pick is another matter!
But if Jython can’t extend a Java class and access its protected members, it can’t really extend a Java class!
Which 1 to pick is another matter! 