chelae 0.1.0

A toolkit for trimming and filtering FASTQ reads.
Documentation 
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//! Small utilities shared across subcommands.

/// Formats a `u64` with comma thousands-separators (e.g. `1,234,567`).
pub(crate) fn fmt_count(n: u64) -> String {
    let s = n.to_string();
    let mut result = String::with_capacity(s.len() + s.len() / 3);
    for (i, ch) in s.chars().enumerate() {
        if i > 0 && (s.len() - i).is_multiple_of(3) {
            result.push(',');
        }
        result.push(ch);
    }
    result
}

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

    #[test]
    fn small() {
        assert_eq!(fmt_count(0), "0");
        assert_eq!(fmt_count(999), "999");
    }

    #[test]
    fn with_commas() {
        assert_eq!(fmt_count(1_000), "1,000");
        assert_eq!(fmt_count(1_234_567), "1,234,567");
        assert_eq!(fmt_count(1_000_000_000), "1,000,000,000");
    }
}