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Using the conditional function
============================================================================================================================================
**07-condition.py**
The `if` function let the user set different processing branches
according to the result of a condition. The syntax is:
.. code-block:: scheme
(if (condition) (then) (else))
The example below uses two conditional statements. The first one
adjusts the duty cycle of a pulse-width-modulation waveform and
the second one split the positive and negative parts of the wave.
A slider, controlling a user variable, sets the gain of the
negative part.
.. code-block:: python
from pyo import *
s = Server().boot()
expression = """
// Width of the duty cycle.
(var #thresh 0.5)
// Gain of the negative part of the waveform.
(var #gain 1)
// Running phase.
(let #sig (~ 172))
// If running phase is below threshold,
// then 1.0, else -1.0
(let #rect (
if (<= #sig #thresh) (1.0) (-1.0)
)
)
// If positive, pass through, else,
// modulated by #gain variable.
(if (>= #rect 0)
(#rect)
(* #gain #rect)
)
"""
expr = Expr(Sig(0), expression, mul=0.5)
expr.editor()
threshold = Sig(0.5)
threshold.ctrl([SLMap(0.01, 0.5, "lin", "value", 0.5)], title="Duty Cycle")
rectifier = Sig(1.0)
rectifier.ctrl([SLMap(0.0, 1.0, "lin", "value", 1.0)], title="Rectifier")
def change():
"Sends new values to user variables in the expression."
expr.setVar(["#thresh", "#gain"], [threshold.get(), rectifier.get()])
# Calls the change() function every 20 ms to update the user variables.
pat = Pattern(change, 0.025).play()
sc = Scope(expr)
pan = Pan(expr).out()
s.gui(locals())
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