Replacing callbacks with generators

# Replacing Callbacks with Generators

## A Case Study in Computer-Assisted Live Music

.br[
[![Matthieu Amiguet](pics/ma.png)](http://www.matthieuamiguet.ch/)   
[![Les Chemins de Traverse](pics/logo-small.png)](http://www.lescheminsdetraverse.net/)
]

]

---

# The Augmented Minstrel

## A Tale of Music, Snakes and Wizardry

---

---

background-image: url(pics/PyconDE_page002.svg), url(pics/parchment.jpg)
class: bottom, center
# The Augmented Minstrel

---

# Passamezzo antico (renaissance tune)

- Matthieu Amiguet, Augmented bass flute solo, Live performance 2013
- Everything is played live - no sound is pre-recorded!

---

---

---

```
wait_for_midi(192,1);

<<< "Record bass!" >>>;
bass.record(1);

wait_for_midi(192,1);

<<< "Let's add a melody!" >>>;
bass.record(0);
bass.loop(1);
bass.recPos() => bass.loopEnd => chords.duration;
bass.recPos() * 3 => mel.duration;
bass.play(1);
mel.record(1);
bass.recPos() * 3 => now;

<<< "Now Chords!" >>>;
mel.record(0);
mel.gain(1.1);
mel.play(1);
chords.feedback(1);
chords.recRamp(.25::second);
chords.record(1);
chords.play(1); 
(bass.recPos() * 3) - .5::second => now;
mel.rampDown(.5::second);
.5::second => now;
```

---

```
*wait_for_midi(192,1);

<<< "Record bass!" >>>;
bass.record(1);

*wait_for_midi(192,1);

```
wait_for_midi(192,1);

<<< "Record bass!" >>>;
bass.record(1);

wait_for_midi(192,1);

---

---

---

# If it quacks like a duck, it might be a python

```python
import pyo

s = pyo.Server(audio='jack', nchnls=1).boot()
s.start()

a = pyo.Input(chnl=0)
fol = pyo.Follower(a, freq=30, mul=4000, add=40)
f = pyo.Biquad(a, freq=fol, q=5, type=2).out()

s.gui()
```

---

- More details on why we chose python+pyo for live music:
- Europython 2019 Talk
- https://www.matthieuamiguet.ch/blog/europython19-talk-online

- ![](pics/europython19-qr.png)

---

```python

def callback():
    # Implement some great feature here!

# Call the function in two seconds
ca = pyo.CallAfter(callback, 2)

# Execute the callback when b1 is pressed on
# the foot controller

tf = pyo.TrigFunc(b1.trig, callback)

```

---

```python

def callback():
    # Implement some great feature here!

# Call the function in two seconds
*ca = pyo.CallAfter(callback, 2)

# Execute the callback when b1 is pressed on
# the foot controller

tf = pyo.TrigFunc(b1.trig, callback)

```

---

```python

def callback():
    # Implement some great feature here!

# Call the function in two seconds
ca = pyo.CallAfter(callback, 2)

# Execute the callback when b1 is pressed on
# the foot controller

*tf = pyo.TrigFunc(b1.trig, callback)

```

---

![](graphs/a_b1_b.dot.svg)

```python
# DOES NOT WORK!!

def a():
    # do whatever a does
    tf = pyo.TrigFunc(b1.trig, b)

def b():
    # do whatever b does
    tf.stop()
```

---

![](graphs/a_b1_b.dot.svg)

```python
*tf = pyo.TrigFunc(b1.trig, b).stop()

def a():
    # do whatever a does
    tf.play()

def b():
    tf.stop()
    # do whatever b does
```

---

![](graphs/wait2s.dot.svg)

```python
tf = pyo.TrigFunc(b1.trig, b).stop()
ca = pyo.CallAfter(2, c).stop()

def a():
    # do whatever a does
    tf.play()
    ca.play()

def b():
    tf.stop()
    ca.stop()
    # do whatever b does
    
def c():
    tf.stop()
    ca.stop()
    # do whatever c does
```

---

---

![](graphs/wait2s.dot.svg)

```python
tf = pyo.TrigFunc(b1.trig, b).stop()
ca = pyo.CallAfter(2, c).stop()

def a():
    # do whatever a does
    tf.play()
    ca.play()

def b():
    tf.stop()
    ca.stop()
    # do whatever b does
    
def c():
    tf.stop()
    ca.stop()
    # do whatever c does
```

---

![](graphs/wait2s.dot.svg)

```python

# do whatever a does

event = wait_until_first_of(   # <------ this does not exist!
    b1, # foot controller button 1
    2 # timeout of 2 seconds
)

if event == 0:
    # do whatever b does
else:
    # do whatever c does

```

---

---

![](pics/oracle.png)

---

---

---

---

![Definition of generator](pics/generators.jpg)

---

```python
def count(max):

n = 1

while n <= max:
        yield n
        n += 1
```

```python-repl
>>> for n in count(3):
...    print(n)
1
2
3
```

```python-repl
>>> c = count(3)
>>> next(c)
1
>>> next(c)
2
>>> next(c)
3
>>> next(c)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration
```

---

```python
def adder():

sum = 0

while True:
        sum += yield sum

```

```python-repl
>>> s = adder()
>>> s.send(None) # execute to first `yield`
0
>>> s.send(1)
1
>>> s.send(2)
3
>>> s.send(3)
6
```

---

```python
# do whatever a does

event = wait_until_first_of(   # <------ this does not exist!
    b1, # foot controller button 1
    2 # timeout of 2 seconds
)

if event == 0:
    # do whatever b does
else:
    # do whatever c does
```

```python
class Example(Scenario):

def setup(self):
        # setup everything here

def steps(self):

# do whatever a does

event = yield b1, 2

if event == 0:
            # do whatever b does
        else:
            # do whatever c does
```

---

```python
# do whatever a does

*event = wait_until_first_of(   # <------ this does not exist!
*   b1, # foot controller button 1
*   2 # timeout of 2 seconds
*)

if event == 0:
    # do whatever b does
else:
    # do whatever c does
```

```python
class Example(Scenario):

def setup(self):
        # setup everything here

def steps(self):

# do whatever a does

*       event = yield b1, 2

if event == 0:
            # do whatever b does
        else:
            # do whatever c does
```

---

```python
class Scenario:

# Max number of TrigFunc's and CallAfter's. 
    # Override in subclasses if needed.
    MAX_TF = 3
    MAX_CA = 1

def __init__(self, max_tf=3):

self.tfs = TrigFuncPool(self.step, self.MAX_TF)
        self.cas = CallAfterPool(self.step, self.MAX_CA)

self.setup(initial=True)
        self._state = self.runner()

# "Bootstrap" the generator
        self.step(None)

def setup(self, initial):
        ''' Override in subclasses. Should be a regular method '''
        raise NotImplementedError

def steps(self):
        ''' Override in subclasses. Should be a generator '''
        raise NotImplementedError
```

---

```python
class Scenario:

# Max number of TrigFunc's and CallAfter's. 
    # Override in subclasses if needed.
    MAX_TF = 3
    MAX_CA = 1

def __init__(self, max_tf=3):

*       self.tfs = TrigFuncPool(self.step, self.MAX_TF)
*       self.cas = CallAfterPool(self.step, self.MAX_CA)

self.setup(initial=True)
        self._state = self.runner()

# "Bootstrap" the generator
        self.step(None)

def setup(self, initial):
        ''' Override in subclasses. Should be a regular method '''
        raise NotImplementedError

def steps(self):
        ''' Override in subclasses. Should be a generator '''
        raise NotImplementedError
```

---

```python
class Scenario:

# Max number of TrigFunc's and CallAfter's. 
    # Override in subclasses if needed.
    MAX_TF = 3
    MAX_CA = 1

def __init__(self, max_tf=3):

self.tfs = TrigFuncPool(self.step, self.MAX_TF)
        self.cas = CallAfterPool(self.step, self.MAX_CA)

*       self.setup(initial=True)
*       self._state = self.runner()

# "Bootstrap" the generator
*       self.step(None)

def setup(self, initial):
        ''' Override in subclasses. Should be a regular method '''
        raise NotImplementedError

def steps(self):
        ''' Override in subclasses. Should be a generator '''
        raise NotImplementedError
```

---

```python
class Scenario:

# Max number of TrigFunc's and CallAfter's. 
    # Override in subclasses if needed.
    MAX_TF = 3
    MAX_CA = 1

def __init__(self, max_tf=3):

self.tfs = TrigFuncPool(self.step, self.MAX_TF)
        self.cas = CallAfterPool(self.step, self.MAX_CA)

self.setup(initial=True)
        self._state = self.runner()

# "Bootstrap" the generator
        self.step(None)

*   def setup(self, initial):
*       ''' Override in subclasses. Should be a regular method '''
*       raise NotImplementedError
*
*   def steps(self):
*       ''' Override in subclasses. Should be a generator '''
*       raise NotImplementedError
```

---

```python
    def step(self, triggering_event_index=0):

self.tfs.stop_all()
        self.cas.stop_all()

wait_for = self._state.send(triggering_event_index)

if wait_for is None: return

if not isinstance(wait_for, tuple):
            wait_for = (wait_for,)

for i, event in enumerate(wait_for):

match event:

case Number(): # wait for i seconds
                    self.cas.start_new(event, i)
                case fc.Press(): # wait for SoftStep Button Press
                    self.tfs.start_new(event.trig, i)
                case pyo.PyoObject(): # wait for generic pyo Trigger
                    self.tfs.start_new(event, i)
                case _:
                    print('Unknown transition type!')

```

---

```python
    def step(self, triggering_event_index=0):

*       self.tfs.stop_all()
*       self.cas.stop_all()

wait_for = self._state.send(triggering_event_index)

if wait_for is None: return

if not isinstance(wait_for, tuple):
            wait_for = (wait_for,)

for i, event in enumerate(wait_for):

match event:

```

---

```python
    def step(self, triggering_event_index=0):

self.tfs.stop_all()
        self.cas.stop_all()

*       wait_for = self._state.send(triggering_event_index)

if wait_for is None: return

if not isinstance(wait_for, tuple):
            wait_for = (wait_for,)

for i, event in enumerate(wait_for):

match event:

```

---

```python
    def step(self, triggering_event_index=0):

self.tfs.stop_all()
        self.cas.stop_all()

wait_for = self._state.send(triggering_event_index)

if wait_for is None: return

*       if not isinstance(wait_for, tuple):
*           wait_for = (wait_for,)
*
*       for i, event in enumerate(wait_for):
*
*           match event:
*
*               case Number(): # wait for i seconds
*                   self.cas.start_new(event, i)
*               case fc.Press(): # wait for SoftStep Button Press
*                   self.tfs.start_new(event.trig, i)
*               case pyo.PyoObject(): # wait for generic pyo Trigger
*                   self.tfs.start_new(event, i)
*               case _:
*                   print('Unknown transition type!')
```
---

```python
    def step(self, triggering_event_index=0):

self.tfs.stop_all()
        self.cas.stop_all()

wait_for = self._state.send(triggering_event_index)

if wait_for is None: return

if not isinstance(wait_for, tuple):
            wait_for = (wait_for,)

for i, event in enumerate(wait_for):

match event:

```

---

```python
    def runner(self):
        ''' Wrapper around self.steps to manage resets and scenario ending.
        Without it we would have to handle it in the subclass' steps().'''

while 1:
            try:
                yield from self.steps()
                print('Scenario is over.')
                yield # keep scenario "alive" to be able to restart it
            except ResetScenario:
                self.setup(initial=False)
                self._state = self.runner()
                self.step(None)

def restart(self):

self._state.throw(ResetScenario())
```

---

---

---

```python
while True:

display('REC ' + loop.name)
    fc.led_off(1)()
    ...
    loop.rec()

if (yield 14 * clic_dur, b2) == 1:
        loop.stop_rec()
        display('CANCELED ' + loop.name)
        ...
        yield b1
        continue

loop.stop_rec()
    ...

display(loop.name + ' OK')
    if (next:=(yield b1, b8, b2)) == 2:
        ...
        display('CANCELED ' + loop.name)
        yield b1
        continue
    ...
    break
```

---

```python
while True:

display('REC ' + loop.name)
    fc.led_off(1)()
    ...
*   loop.rec()
*
*   if (yield 14 * clic_dur, b2) == 1:
*       loop.stop_rec()
*       display('CANCELED ' + loop.name)
*       ...
*       yield b1
*       continue
*
*   loop.stop_rec()
    ...

display(loop.name + ' OK')
    if (next:=(yield b1, b8, b2)) == 2:
        ...
        display('CANCELED ' + loop.name)
        yield b1
        continue
    ...
    break
```

---

```python
while True:

display('REC ' + loop.name)
    fc.led_off(1)()
    ...
    loop.rec()
 
    if (yield 14 * clic_dur, b2) == 1:
        loop.stop_rec()
        display('CANCELED ' + loop.name)
        ...
        yield b1
        continue

loop.stop_rec()
    ...

display(loop.name + ' OK')
*   if (next:=(yield b1, b8, b2)) == 2:
*       ...
*       display('CANCELED ' + loop.name)
*       yield b1
*       continue
    ...
    break
```

---

---

```python
*for loop in [bass] + chords + [hymn]:
    while True:

display('REC ' + loop.name)
        fc.led_off(1)()
        ...
        loop.rec()
     
        if (yield 14 * clic_dur, b2) == 1:
            loop.stop_rec()
            display('CANCELED ' + loop.name)
            ...
            yield b1
            continue

loop.stop_rec()
        ...

display(loop.name + ' OK')
        if (next:=(yield b1, b8, b2)) == 2:
            ...
            display('CANCELED ' + loop.name)
            yield b1
            continue
        ...
        break
```

---

---

```python
yield b1
for loop in [bass] + chords + [hymn]:
    while True:
        # REC
        if (yield 14 * clic_dur, b2) == 1:
            # CANCEL
            continue
        # STOP_REC
        if (next:=(yield b1, b8, b2)) == 2:
            # CANCEL
            yield b1
            continue
        break
while True:
    if next == 1: # b8 was pressed
        # PLAY WITH HYMN
    else:
        # PLAY WITHOUT HYMN
    yield b1, b8
    # STOP
    next = yield b1, b8
```

---

---

- Digital Analogies (excerpt), Live performance 2022
- Pierre-Yves Diacon, Dance // Matthieu Amiguet, Augmented Harpejji

---

---

# Questions?

- Find code, references, and details on https://www.matthieuamiguet.ch/blog/pyconde24

###

- The *Dragonfly* album is available on all major streaming platforms (if you want to support
majors) or on [bandcamp](https://lescheminsdetraverse.bandcamp.com/album/dragonfly) (if you want to support artists).

###

- All music by [Les Chemins de Traverse](https://www.lescheminsdetraverse.net/)
- Drawings by [Matthieu Amiguet](https://www.matthieuamiguet.ch/)
- parchment background by [Devontt on Flickr](https://www.flickr.com/photos/devontt/167285657/in/photostream/) (CC-BY)

.br[
[![Matthieu Amiguet](pics/ma.png)](http://www.matthieuamiguet.ch/)   
[![Les Chemins de Traverse](pics/logo-small.png)](http://www.lescheminsdetraverse.net/)
]