Tropical semi-ring definition in Rust.

tropical.rs

use num::{One, Zero};
use std::ops;

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum Tropical {
    Value(u64),
    Infty,
}

impl Zero for Tropical {
    fn zero() -> Self {
        Self::Infty
    }

    fn is_zero(&self) -> bool {
        matches!(self, Tropical::Infty)
    }
}
impl One for Tropical {
    fn one() -> Self {
        Self::Value(0)
    }
}

impl ops::Add for Tropical {
    type Output = Self;

    fn add(self, rhs: Self) -> Self::Output {
        std::cmp::min(self, rhs)
    }
}
impl ops::AddAssign for Tropical {
    fn add_assign(&mut self, rhs: Self) {
        *self = *self + rhs;
    }
}

impl ops::Mul for Tropical {
    type Output = Self;

    fn mul(self, rhs: Self) -> Self::Output {
        match (self, rhs) {
            (Tropical::Value(l), Tropical::Value(r)) => Tropical::Value(l + r),
            _ => Tropical::Infty,
        }
    }
}
impl ops::MulAssign for Tropical {
    fn mul_assign(&mut self, rhs: Self) {
        *self = *self * rhs;
    }
}