use std::{
    fmt::*,
    ops::{Add, Div, Mul, Sub},
};

#[derive(Debug, Copy, Clone)]
pub enum LispNumber {
    Integer(i64),
    Float(f64),
}

impl Add for LispNumber {
    type Output = Self;
    fn add(self, rhs: Self) -> Self::Output {
        use LispNumber::*;
        match (self, rhs) {
            (Integer(a), Integer(b)) => Integer(a + b),
            (Float(a), Integer(b)) => Float(a + b as f64),
            (Integer(a), Float(b)) => Float(a as f64 + b),
            (Float(a), Float(b)) => Float(a + b),
        }
    }
}

impl Sub for LispNumber {
    type Output = Self;
    fn sub(self, rhs: Self) -> Self::Output {
        use LispNumber::*;
        match (self, rhs) {
            (Integer(a), Integer(b)) => Integer(a - b),
            (Float(a), Integer(b)) => Float(a - b as f64),
            (Integer(a), Float(b)) => Float(a as f64 - b),
            (Float(a), Float(b)) => Float(a - b),
        }
    }
}

impl Mul for LispNumber {
    type Output = Self;
    fn mul(self, rhs: Self) -> Self::Output {
        use LispNumber::*;
        match (self, rhs) {
            (Integer(a), Integer(b)) => Integer(a * b),
            (Float(a), Integer(b)) => Float(a * b as f64),
            (Integer(a), Float(b)) => Float(a as f64 * b),
            (Float(a), Float(b)) => Float(a * b),
        }
    }
}

impl PartialEq for LispNumber {
    fn eq(&self, other: &Self) -> bool {
        use LispNumber::*;
        match (self, other) {
            (Integer(a), Integer(b)) => *a == *b,
            (Float(a), Integer(b)) => *a == *b as f64,
            (Integer(a), Float(b)) => *a as f64 == *b,
            (Float(a), Float(b)) => *a == *b,
        }
    }
}

impl Display for LispNumber {
    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
        match self {
            LispNumber::Integer(v) => write!(f, "{}", v),
            LispNumber::Float(v) => write!(f, "{}", v),
        }
    }
}