From 8c75506f2275c215d45dcccf52340da8717c6fa5 Mon Sep 17 00:00:00 2001 From: Michael Lamparski Date: Thu, 21 Jul 2016 21:35:10 -0400 Subject: [PATCH] Ratio::recip now corrects sign and fails for zero --- rational/src/lib.rs | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/rational/src/lib.rs b/rational/src/lib.rs index db758bf..ec2ee15 100644 --- a/rational/src/lib.rs +++ b/rational/src/lib.rs @@ -135,9 +135,16 @@ impl Ratio { } /// Returns the reciprocal. + /// + /// Fails if the `Ratio` is zero. #[inline] pub fn recip(&self) -> Ratio { - Ratio::new_raw(self.denom.clone(), self.numer.clone()) + match self.numer.cmp(&T::zero()) { + cmp::Ordering::Equal => panic!("numerator == 0"), + cmp::Ordering::Greater => Ratio::new_raw(self.denom.clone(), self.numer.clone()), + cmp::Ordering::Less => Ratio::new_raw(T::zero() - self.denom.clone(), + T::zero() - self.numer.clone()) + } } /// Rounds towards minus infinity. @@ -669,6 +676,10 @@ mod test { numer: 2, denom: 1, }; + pub const _NEG2: Rational = Ratio { + numer: -2, + denom: 1, + }; pub const _1_2: Rational = Ratio { numer: 1, denom: 2, @@ -1007,6 +1018,16 @@ mod test { assert_eq!(_1_2 * _1_2.recip(), _1); assert_eq!(_3_2 * _3_2.recip(), _1); assert_eq!(_NEG1_2 * _NEG1_2.recip(), _1); + + assert_eq!(_3_2.recip(), _2_3); + assert_eq!(_NEG1_2.recip(), _NEG2); + assert_eq!(_NEG1_2.recip().denom(), &1); + } + + #[test] + #[should_panic = "== 0"] + fn test_recip_fail() { + let _a = Ratio::new(0, 1).recip(); } #[test]