rusty-numbers/src/lib.rs

#![forbid(unsafe_code)]

use std::ops::{
    Add, AddAssign, BitAnd, BitAndAssign, BitOr, BitOrAssign, BitXor, BitXorAssign, Div, DivAssign,
    Mul, MulAssign, Not, Rem, RemAssign, Shl, ShlAssign, Shr, ShrAssign, Sub, SubAssign,
};

pub mod bigint;
pub mod rational;
pub mod seq;

/// A Trait representing unsigned integer primitives
pub trait Unsigned:
    Add
    + AddAssign
    + BitAnd
    + BitAndAssign
    + BitOr
    + BitOrAssign
    + BitXor
    + BitXorAssign
    + Div
    + DivAssign
    + Mul
    + MulAssign
    + Rem
    + RemAssign
    + Copy
    + Shl
    + ShlAssign
    + Shr
    + ShrAssign
    + Sub
    + SubAssign
    + Eq
    + Ord
    + Not
{
    /// Find the greatest common denominator of two numbers
    fn gcd(a: Self, b: Self) -> Self;

    /// Find the least common multiple of two numbers
    fn lcm(a: Self, b: Self) -> Self;

    /// The maximum value of the type
    fn max_value() -> Self;

    /// Is this a zero value?
    fn is_zero(self) -> bool;
}

#[derive(Debug, Copy, Clone, PartialEq, Eq)]
pub enum Sign {
    Positive,
    Negative,
}

impl Default for Sign {
    fn default() -> Self {
        Sign::Positive
    }
}

impl Not for Sign {
    type Output = Sign;

    fn not(self) -> Self::Output {
        match self {
            Self::Positive => Self::Negative,
            Self::Negative => Self::Positive,
        }
    }
}

macro_rules! impl_unsigned {
    ($Type: ty) => {
        impl Unsigned for $Type {
            fn gcd(a: $Type, b: $Type) -> $Type {
                if a == b {
                    return a;
                } else if a == 0 {
                    return b;
                } else if b == 0 {
                    return a;
                }

                let a_even = a % 2 == 0;
                let b_even = b % 2 == 0;

                if a_even {
                    if b_even {
                        // Both a & b are even
                        return Self::gcd(a >> 1, b >> 1) << 1;
                    } else if !b_even {
                        // b is odd
                        return Self::gcd(a >> 1, b);
                    }
                }

                // a is odd, b is even
                if (!a_even) && b_even {
                    return Self::gcd(a, b >> 1);
                }

                if a > b {
                    return Self::gcd((a - b) >> 1, b);
                }

                Self::gcd((b - a) >> 1, a)
            }

            fn lcm(a: $Type, b: $Type) -> $Type {
                if (a == 0 && b == 0) {
                    return 0;
                }

                a * b / Self::gcd(a, b)
            }

            fn max_value() -> $Type {
                <$Type>::max_value()
            }

            fn is_zero(self) -> bool {
                self == 0
            }
        }
    };
}
impl_unsigned!(u8);
impl_unsigned!(u16);
impl_unsigned!(u32);
impl_unsigned!(u64);
impl_unsigned!(u128);
impl_unsigned!(usize);

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

    #[test]
    fn test_gcd() {
        assert_eq!(u8::gcd(2, 2), 2);
        assert_eq!(u16::gcd(36, 48), 12);
    }
}