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pub mod categorical;
pub mod numeric;
pub mod string;

pub struct Builder;

impl Builder {
    pub fn numeric<I: numeric::Numeric>(metric: &'static str) -> fn(&[I], &[I]) -> I {
        match metric {
            "euclidean" => numeric::euclidean,
            "euclideansq" => numeric::euclideansq,
            _ => panic!("{} is not a numeric distance function!", metric),
        }
    }

    pub fn categorical<I: categorical::Categorical>(metric: &'static str) -> fn(&[I], &[I]) -> I {
        match metric {
            "hamming" => categorical::hamming,
            _ => panic!("{} is not a categorical distance function!", metric),
        }
    }
}

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

    #[test]
    fn test_build_numeric() {
        let x = [1., 2., 3.];
        let metric = Builder::numeric("euclidean");
        assert_eq!(metric(&x, &x), 0.);
    }

    #[test]
    fn test_hamming() {
        let x = [1, 2, 3];
        let y = [1, 1, 1];
        assert_eq!(categorical::hamming(&x, &y), 2);
    }

    #[test]
    fn test_manhattan() {
        let x: [f64; 3] = [1., 2., 3.];
        let y: [f64; 3] = [1., 1., 1.];
        assert_eq!(numeric::manhattan(&x, &y), 3.);
    }

    #[test]
    fn test_cosine() {
        let x = [1.0, 1.0, 1.0];
        let y = [1.0, 1.0, 1.0];
        assert!(approx_eq!(f64, numeric::cosine(&x, &y), 1.0, ulps = 2));
    }

    #[test]
    fn test_euclidean() {
        let x = [0.0, 3.0];
        let y = [4.0, 0.0];
        assert_eq!(numeric::euclidean(&x, &y), 5.0);
    }

    #[test]
    fn test_euclideansq() {
        let x = [0.0, 3.0];
        let y = [4.0, 0.0];
        assert_eq!(numeric::euclideansq(&x, &y), 25.0);
    }
}