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pub trait DigitUtils {
    fn digit(self) -> u32;
    fn leftmost_digit(self) -> u8;
    fn rightmost_digit(self) -> u8;
}

macro_rules! impl_digit_utils(($($ty:ty),*) => {
    $(
        impl DigitUtils for $ty {
            fn digit(self) -> u32 {
                (self as f64).log10().trunc() as u32 + 1
            }

            fn leftmost_digit(self) -> u8 {
                let digit = self.digit() - 1;
                (self / (10 as $ty).pow(digit)) as u8
            }

            fn rightmost_digit(self) -> u8 {
                (self % 10) as u8
            }
        }
    )*
});

impl_digit_utils!(u64, u32, i64, i32, usize, isize);

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn u64_utils_test() -> () {
        assert_eq!(1u64.digit(), 1);
        assert_eq!(12u64.digit(), 2);

        assert_eq!(1u64.leftmost_digit(), 1);
        assert_eq!(200u64.leftmost_digit(), 2);

        assert_eq!(10u64.rightmost_digit(), 0);
        assert_eq!(202u64.rightmost_digit(), 2);
    }
    #[test]
    fn u32_utils_test() -> () {
        assert_eq!(1u32.digit(), 1);
        assert_eq!(12u32.digit(), 2);

        assert_eq!(1u32.leftmost_digit(), 1);
        assert_eq!(200u32.leftmost_digit(), 2);

        assert_eq!(10u32.rightmost_digit(), 0);
        assert_eq!(202u32.rightmost_digit(), 2);
    }
    #[test]
    fn i64_utils_test() -> () {
        assert_eq!(1i64.digit(), 1);
        assert_eq!(12i64.digit(), 2);

        assert_eq!(1i64.leftmost_digit(), 1);
        assert_eq!(200i64.leftmost_digit(), 2);

        assert_eq!(10i64.rightmost_digit(), 0);
        assert_eq!(202i64.rightmost_digit(), 2);
    }
    #[test]
    fn i32_utils_test() -> () {
        assert_eq!(1i32.digit(), 1);
        assert_eq!(12i32.digit(), 2);

        assert_eq!(1i32.leftmost_digit(), 1);
        assert_eq!(200i32.leftmost_digit(), 2);

        assert_eq!(10i32.rightmost_digit(), 0);
        assert_eq!(202i32.rightmost_digit(), 2);
    }
    #[test]
    fn usize_utils_test() -> () {
        assert_eq!(1usize.digit(), 1);
        assert_eq!(12usize.digit(), 2);

        assert_eq!(1usize.leftmost_digit(), 1);
        assert_eq!(200usize.leftmost_digit(), 2);

        assert_eq!(10usize.rightmost_digit(), 0);
        assert_eq!(202usize.rightmost_digit(), 2);
    }
    #[test]
    fn isize_utils_test() -> () {
        assert_eq!(1isize.digit(), 1);
        assert_eq!(12isize.digit(), 2);

        assert_eq!(1isize.leftmost_digit(), 1);
        assert_eq!(200isize.leftmost_digit(), 2);

        assert_eq!(10isize.rightmost_digit(), 0);
        assert_eq!(202isize.rightmost_digit(), 2);
    }
}