yagi 0.1.3

Batteries-included DSP library
Documentation 
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use crate::error::{Error, Result};
use rand::Rng;

/// Uniform random number generator
pub fn randf() -> f32 {
    let mut rng = rand::thread_rng();
    rng.gen::<f32>()
}

/// Uniform random number probability distribution function
pub fn randf_pdf(x: f32) -> f32 {
    if x < 0.0 || x > 1.0 {
        0.0
    } else {
        1.0
    }
}

/// Uniform random number cumulative distribution function
pub fn randf_cdf(x: f32) -> f32 {
    if x < 0.0 {
        0.0
    } else if x > 1.0 {
        1.0
    } else {
        x
    }
}

/// Uniform random number generator with arbitrary bounds
pub fn randuf(a: f32, b: f32) -> Result<f32> {
    if a >= b {
        return Err(Error::Range(format!("randuf({},{}) has invalid range", a, b)));
    }

    Ok(a + (b - a) * randf())
}

/// Uniform random number probability distribution function
pub fn randuf_pdf(x: f32, a: f32, b: f32) -> Result<f32> {
    if a >= b {
        return Err(Error::Range(format!("randuf_pdf({},{},{}) has invalid range", x, a, b)));
    }

    Ok(if x < a || x > b { 0.0 } else { 1.0 / (b - a) })
}

/// Uniform random number cumulative distribution function
pub fn randuf_cdf(x: f32, a: f32, b: f32) -> Result<f32> {
    if a >= b {
        return Err(Error::Range(format!("randuf_cdf({},{},{}) has invalid range", x, a, b)));
    }

    Ok(if x < a {
        0.0
    } else if x > b {
        1.0
    } else {
        (x - a) / (b - a)
    })
}

#[cfg(test)]
mod tests {
    use super::*;
    use test_macro::autotest_annotate;
    use approx::assert_relative_eq;



    #[test]
    #[autotest_annotate(autotest_randf)]
    fn test_randf() {
        const NUM_TRIALS: usize = 100_000;
        const TOL: f32 = 0.1;

        let mut m1: f32 = 0.0;
        let mut m2: f32 = 0.0;

        for _ in 0..NUM_TRIALS {
            let x = randf();
            m1 += x;
            m2 += x * x;
        }

        m1 /= NUM_TRIALS as f32;
        m2 = (m2 / NUM_TRIALS as f32) - m1 * m1;

        println!("m1 = {:.6} (expected 0.5)", m1);
        println!("m2 = {:.6} (expected 1/12 = 0.0833333)", m2);

        assert_relative_eq!(m1, 0.5f32, epsilon = TOL);
        assert_relative_eq!(m2, 1.0f32 / 12.0f32, epsilon = TOL);
    }
}