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Fixed floating point issue with asinh function #63698

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merged 5 commits into from
Aug 27, 2019
Merged

Fixed floating point issue with asinh function #63698

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92f08b7
Merge pull request #1 from rust-lang/master
Phosphorus15 Aug 19, 2019
c456934
Added negative cases for `asinh` according to IEEE-754.
Phosphorus15 Aug 19, 2019
64e3a10
test cases for both `f32` and `f64` on asinh(-0.0)
Phosphorus15 Aug 19, 2019
535efa4
Used `copysign` to avoid unnecessary branches.
Phosphorus15 Aug 20, 2019
e33d870
Refined implementations of `asinh` and `acosh`
Phosphorus15 Aug 20, 2019
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8 changes: 4 additions & 4 deletions src/libstd/f32.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -908,10 +908,9 @@ impl f32 {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn asinh(self) -> f32 {
if self == NEG_INFINITY {
NEG_INFINITY
} else {
(self + ((self * self) + 1.0).sqrt()).ln()
match self {
x if x == NEG_INFINITY => NEG_INFINITY,
x => (x + ((x * x) + 1.0).sqrt()).ln().copysign(self)
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I would prefer to use if-else directly.

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Yea, that sounds reasonable, maybe consider changing the original acosh BTW?

pub fn acosh(self) -> f64 {
        match self {
            x if x < 1.0 => NAN,
            x => (x + ((x * x) - 1.0).sqrt()).ln(),
        }
    }

}
}

Expand Down Expand Up @@ -1488,6 +1487,7 @@ mod tests {
assert_eq!(inf.asinh(), inf);
assert_eq!(neg_inf.asinh(), neg_inf);
assert!(nan.asinh().is_nan());
assert!((-0.0f32).asinh().is_sign_negative()); // issue 63271
assert_approx_eq!(2.0f32.asinh(), 1.443635475178810342493276740273105f32);
assert_approx_eq!((-2.0f32).asinh(), -1.443635475178810342493276740273105f32);
}
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8 changes: 4 additions & 4 deletions src/libstd/f64.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -831,10 +831,9 @@ impl f64 {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn asinh(self) -> f64 {
if self == NEG_INFINITY {
NEG_INFINITY
} else {
(self + ((self * self) + 1.0).sqrt()).ln()
match self {
x if x == NEG_INFINITY => NEG_INFINITY,
x => (x + ((x * x) + 1.0).sqrt()).ln().copysign(self)
}
}

Expand Down Expand Up @@ -1434,6 +1433,7 @@ mod tests {
assert_eq!(inf.asinh(), inf);
assert_eq!(neg_inf.asinh(), neg_inf);
assert!(nan.asinh().is_nan());
assert!((-0.0f64).asinh().is_sign_negative()); // issue 63271
assert_approx_eq!(2.0f64.asinh(), 1.443635475178810342493276740273105f64);
assert_approx_eq!((-2.0f64).asinh(), -1.443635475178810342493276740273105f64);
}
Expand Down