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use super::{SamplesPerSecond, Hz};
pub type Phase = f32; // Phase will always be between 0.0 and 1.0.
/// Phase stays between 0.0 and 1.0 and represents position on the axis of time
/// for a given wave form. Since audio signals are periodic, we can just calculate
/// the first cycle of a wave repeatedly. This also prevents pitch drift caused by
/// floating point errors over time.
pub struct Phasor {
pub phase: Phase,
pub frequency: Hz,
pub sample_rate: SamplesPerSecond,
}
impl Phasor {
pub fn new(frequency: Hz, sample_rate: SamplesPerSecond) -> Self {
Self { phase: 0.0, frequency, sample_rate }
}
}
impl Iterator for Phasor {
type Item = Phase;
fn next(&mut self) -> Option<Self::Item> {
self.phase = (self.phase + self.frequency / self.sample_rate) % 1.0;
Some(self.phase)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_produces_expected_next_value() {
let mut phasor = Phasor::new(10.0, 100.0);
assert_eq!(phasor.next(), Some(0.1))
}
#[test]
fn it_produces_expected_next_values() {
let phasor = Phasor::new(10.0, 100.0);
let taken_iterator = phasor.take(11);
assert_eq!(taken_iterator.last(), Some(0.1))
// assert_eq!([0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 0.1], next)
}
}
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