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use std::fmt;
use std::f32;
#[derive(Debug, Clone, Copy)]
pub struct Pitch {
pub hz: f32
}
impl Pitch {
pub fn new(hz: f32) -> Pitch {
Pitch {
hz: hz
}
}
fn midi_number(&self) -> f32 {
69.0 + 12.0 * (self.hz / 440.0).log2()
}
pub fn cents_error(&self) -> f32 {
if !self.hz.is_finite() {
return f32::NAN;
}
let midi_number = self.midi_number();
let cents = (midi_number - midi_number.floor()) * 100.0;
if cents >= 50.0 {
cents - 100.0
}
else {
cents
}
}
}
impl fmt::Display for Pitch {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
if self.hz <= 0.0 || !self.hz.is_finite() {
write!(f, "")
} else {
let pitch_names = [
"C",
"C♯",
"D",
"E♭",
"E",
"F",
"F♯",
"G",
"G♯",
"A",
"B♭",
"B"
];
//midi_number of 0 is C-1.
let rounded_pitch = self.midi_number().round() as i32;
let name = pitch_names[rounded_pitch as usize % pitch_names.len()];
let octave = rounded_pitch / pitch_names.len() as i32 - 1;
write!(f, "{: <2}{}", name, octave)
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn a4_is_correct() {
assert_eq!(format!("{}", Pitch::new(440.0)), "A 4");
}
#[test]
fn a2_is_correct() {
assert_eq!(format!("{}", Pitch::new(110.0)), "A 2");
}
#[test]
fn c4_is_correct() {
assert_eq!(format!("{}", Pitch::new(261.63)), "C 4");
}
#[test]
fn f5_is_correct() {
assert_eq!(format!("{}", Pitch::new(698.46)), "F 5");
}
}
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