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feat: implement CheckedNeg for Ratio #152

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feat: implement CheckedNeg for Ratio #152

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13 changes: 12 additions & 1 deletion src/ops.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use super::Ratio;
use core::ops::{Add, Div, Mul, Neg, Rem, Sub};

use num_integer::Integer;
use num_traits::{CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, Inv, One, Zero};
use num_traits::{CheckedAdd, CheckedDiv, CheckedMul, CheckedNeg, CheckedSub, Inv, One, Zero};

macro_rules! forward_ref_ref_binop {
(impl $imp:ident, $method:ident) => {
Expand Down Expand Up @@ -273,6 +273,17 @@ checked_arith_impl!(impl CheckedAdd, checked_add);
// a/b - c/d = (lcm/b*a - lcm/d*c)/lcm, where lcm = lcm(b,d)
checked_arith_impl!(impl CheckedSub, checked_sub);

// -(a/b) = (-a)/b, so only the numerator can overflow
impl<T> CheckedNeg for Ratio<T>
where
T: Clone + Integer + CheckedNeg,
{
#[inline]
fn checked_neg(&self) -> Option<Ratio<T>> {
Some(Ratio::new_raw(self.numer.checked_neg()?, self.denom.clone()))
}
}

impl<T> Neg for Ratio<T>
where
T: Clone + Integer + Neg<Output = T>,
Expand Down
11 changes: 10 additions & 1 deletion src/tests/arith.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use super::super::{Ratio, Rational64};
use super::{to_big, _0, _1, _1_2, _2, _3_2, _5_2, _MAX, _MAX_M1, _MIN, _MIN_P1, _NEG1_2};
use core::fmt::Debug;
use num_integer::Integer;
use num_traits::{Bounded, CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, NumAssign};
use num_traits::{Bounded, CheckedAdd, CheckedDiv, CheckedMul, CheckedNeg, CheckedSub, NumAssign};

#[test]
fn test_add() {
Expand Down Expand Up @@ -398,6 +398,15 @@ fn test_neg() {
test(_1_2, _NEG1_2);
test(-_1, _1);
}

#[test]
fn test_checked_neg() {
assert_eq!(_0.checked_neg(), Some(_0));
assert_eq!(_1_2.checked_neg(), Some(_NEG1_2));
assert_eq!(_NEG1_2.checked_neg(), Some(_1_2));
// Negating the numerator i64::MIN overflows.
assert_eq!(Ratio::new(i64::MIN, 3).checked_neg(), None);
}
#[test]
#[allow(clippy::eq_op)]
fn test_zero() {
Expand Down