diff options
| -rw-r--r-- | src/libcore/num/f32.rs | 4 | ||||
| -rw-r--r-- | src/libcore/num/f64.rs | 3 | ||||
| -rw-r--r-- | src/libstd/f32.rs | 1 |
3 files changed, 7 insertions, 1 deletions
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs index 207df84d080..3586fa5442f 100644 --- a/src/libcore/num/f32.rs +++ b/src/libcore/num/f32.rs @@ -239,7 +239,9 @@ impl Float for f32 { /// Converts to degrees, assuming the number is in radians. #[inline] fn to_degrees(self) -> f32 { - self * (180.0f32 / consts::PI) + // Use a constant for better precision. + const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32; + self * PIS_IN_180 } /// Converts to radians, assuming the number is in degrees. diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs index 9206132e8b4..64c0d508b38 100644 --- a/src/libcore/num/f64.rs +++ b/src/libcore/num/f64.rs @@ -237,6 +237,9 @@ impl Float for f64 { /// Converts to degrees, assuming the number is in radians. #[inline] fn to_degrees(self) -> f64 { + // The division here is correctly rounded with respect to the true + // value of 180/π. (This differs from f32, where a constant must be + // used to ensure a correctly rounded result.) self * (180.0f64 / consts::PI) } diff --git a/src/libstd/f32.rs b/src/libstd/f32.rs index 9810dede618..ecf68f29d6f 100644 --- a/src/libstd/f32.rs +++ b/src/libstd/f32.rs @@ -1531,6 +1531,7 @@ mod tests { assert!(nan.to_degrees().is_nan()); assert_eq!(inf.to_degrees(), inf); assert_eq!(neg_inf.to_degrees(), neg_inf); + assert_eq!(1_f32.to_degrees(), 57.2957795130823208767981548141051703); } #[test] |