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use super::{Millisecond, Amplitude, SamplesPerSecond};
use super::utils::*;
pub struct Line {
index: u32,
samples: u32,
slope: f32,
y_intercept: f32,
}
impl Line {
pub fn new(
start: Amplitude, end: Amplitude, duration: Millisecond, sample_rate: SamplesPerSecond
) -> Self {
let number_of_samples = ms_to_samples(duration, sample_rate);
Self {
index: 0,
slope: slope(start, end, number_of_samples),
samples: number_of_samples,
y_intercept: start,
}
}
}
impl Iterator for Line {
type Item = Amplitude;
fn next(&mut self) -> Option<Self::Item> {
let idx = self.index;
let val = self.slope * idx as f32 + self.y_intercept;
self.index += 1;
if idx <= self.samples {
Some(val)
} else {
None
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn it_calculates_a_slope() {
let expected = 0.5;
let slope = slope(0.0, 0.5, 1);
assert_eq! (slope, expected)
}
#[test]
fn it_calculates_the_next_values() {
let mut line = Line::new(0.0, 0.5, 1, 5000.0);
assert_eq!(line.next(), Some(0.0));
assert_eq!(line.next(), Some(0.1));
assert_eq!(line.next(), Some(0.2));
assert_eq!(line.next(), Some(0.3));
assert_eq!(line.next(), Some(0.4));
assert_eq!(line.next(), Some(0.5));
assert_eq!(line.next(), None);
}
}
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