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use std::cmp::{PartialOrd};
use ::num_traits::{Trig, ArithmeticOps, FractionOps};
/// A data structure representing a sinusoid. AKA the sin or cos functions.
///
/// The general formula for a sinusoid is A cos(2πf + θ)
///
/// The number type is generic, but realistically it's only useful for
/// floats.
pub struct Sinusoid<T> {
amplitude: T,
frequency: T,
phase: T
}
impl<T> Sinusoid<T> {
pub fn new(amplitude:T, frequency: T, phase: T) -> Sinusoid<T> {
Sinusoid {
amplitude: amplitude,
frequency: frequency,
phase: phase
}
}
}
impl<T> Sinusoid<T> where T: FractionOps + Copy {
/// The period is the time taken for each repetition of the
/// sinusoid
///
/// ```
/// use worthe_signals::sinusoid::Sinusoid;
/// use std::f32;
///
/// let sinusoid = Sinusoid::new(1.0 as f32, 0.5, 0.0);
/// assert!((sinusoid.period()-2.0) < f32::EPSILON);
/// ```
pub fn period(&self) -> T {
self.frequency.recip()
}
}
impl<T> Sinusoid<T> where T: FractionOps + ArithmeticOps + Trig + Copy {
/// Frequency can be considered in terms of the signal's number of
/// repetitions per second (referred to just as the frequency), or
/// the frequency in radians.
/// ```
/// use worthe_signals::sinusoid::Sinusoid;
/// use std::f32;
///
/// let sinusoid = Sinusoid::new(1.0 as f32, 1.0, 0.0);
/// assert!((sinusoid.radial_frequency()-2.0*f32::consts::PI) < f32::EPSILON);
/// ```
pub fn radial_frequency(&self) -> T {
T::two_pi()*self.frequency
}
/// A sinusoid can be sampled to get its value at a given point in
/// time.
///
/// ```
/// use worthe_signals::sinusoid::Sinusoid;
/// use std::f32;
///
/// let sinusoid = Sinusoid::new(1.0 as f32, 1.0, -f32::consts::FRAC_PI_2); //AKA sin
/// assert!((sinusoid.sample(0.0)-0.0) < f32::EPSILON);
/// assert!((sinusoid.sample(0.25)-1.0) < f32::EPSILON);
/// assert!((sinusoid.sample(0.5)-0.0) < f32::EPSILON);
/// assert!((sinusoid.sample(0.75)+1.0) < f32::EPSILON);
/// assert!((sinusoid.sample(1.0)-0.0) < f32::EPSILON);
/// ```
pub fn sample(&self, t: T) -> T {
(self.radial_frequency()*(t%self.period()) + self.phase).cos() * self.amplitude
}
}
impl<T> Sinusoid<T> where T: FractionOps + ArithmeticOps + From<u16> + Trig + Copy + PartialOrd {
/// Sometimes, it's useful to sample at all of the points in a range
///
/// Start value is inclusive. End value is exclusive.
///
/// ```
/// use worthe_signals::sinusoid::Sinusoid;
/// use std::f32;
///
/// let sinusoid = Sinusoid::new(1.0 as f32, 1.0, -f32::consts::FRAC_PI_2); //AKA sin
/// let samples = sinusoid.sample_range(0.0, 100.0, 4.0);
/// assert_eq!(samples.len(), 400);
/// for i in (0..100).map(|i| i*4) {
/// assert!((samples[i+0]-0.0) < f32::EPSILON, "Sample {} was {}", i+0, samples[i+0]);
/// assert!((samples[i+1]-1.0) < f32::EPSILON, "Sample {} was {}", i+1, samples[i+1]);
/// assert!((samples[i+2]-0.0) < f32::EPSILON, "Sample {} was {}", i+2, samples[i+2]);
/// assert!((samples[i+3]+1.0) < f32::EPSILON, "Sample {} was {}", i+3, samples[i+3]);
/// }
/// ```
pub fn sample_range(&self, start: T, end: T, sample_rate: T) -> Vec<T> {
let mut result = Vec::new();
let mut i: u16 = 0;
loop {
let t = start + T::from(i)/sample_rate;
if t >= end {
break;
}
result.push(self.sample(t));
i += 1;
}
result
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::f32;
}
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