Rounds number to the nearest divisor.

round_to_nearest_divisor.rs

use num_traits::cast::AsPrimitive;

/// Rounds number to the nearest divisor.
pub fn round_to_nearest_divisor<T>(num: T, divisor: T) -> T
where
    T: AsPrimitive<f32>,
    f32: AsPrimitive<T>,
{
    let divisor: f32 = divisor.as_();
    let num: f32 = num.as_();
    
    ((num / divisor).round() * divisor).as_()
}

#[cfg(test)]
mod tests {
    use super::*;
    
    #[test]
    fn rounds_correctly() {
        assert_eq!(round_to_nearest_divisor(4, 5), 5);
        assert_eq!(round_to_nearest_divisor(-1, 5), 0);
        assert_eq!(round_to_nearest_divisor(-4, 5), -5);
        assert_eq!(round_to_nearest_divisor(66, 20), 60); 
        assert_eq!(round_to_nearest_divisor(104, 100), 100);
        assert_eq!(round_to_nearest_divisor(104 as usize, 100), 100);
        assert_eq!(round_to_nearest_divisor(8.0, 10.0), 10.0);
    }
}