dnacomb 0.5.0

Count the occurances of structured sequence reads and compare to an expected library
Documentation 
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//! Utility fucntions for use throughout the library
//!
//! Provides a range of utility functions that are needed across modules

/// Calculate the mean of a fastq quality vector
pub fn mean_quality(qual: &[u8]) -> f32 {
    if qual.is_empty() {
        return 0.0;
    };

    let total: u32 = qual.iter().fold(0, |a, e| a + *e as u32);
    total as f32 / qual.len() as f32 - 33.0 // Subtract 33 as Phred scores are shifted 33 in byte codepoints
}

/// Divide x / y or return 0.0 if y == 0
pub fn div_or_zero(x: f32, y: f32) -> f32 {
    if y == 0.0 {
        return 0.0;
    }

    x / y
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_mean_quality() {
        assert_eq!(mean_quality(b"FFFF"), 37.0);
        assert_eq!(mean_quality(b"AAAA"), 32.0);
        assert_eq!(mean_quality(b"!!!!"), 0.0);
        assert_eq!(mean_quality(b"0101"), 15.5);
        assert_eq!(mean_quality(b""), 0.0);
    }

    #[test]
    fn test_division_by_nonzero() {
        assert_eq!(div_or_zero(5.0, 1.0), 5.0);
        assert_eq!(div_or_zero(10.0, 2.0), 5.0);
        assert_eq!(div_or_zero(24.0, 3.0), 24.0 / 3.0);
        assert_eq!(div_or_zero(13.0, 2.5), 13.0 / 2.5);
    }

    #[test]
    fn test_division_by_zero() {
        assert_eq!(div_or_zero(1.0, 0.0), 0.0);
    }
}