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doc: show that f32::log and f64::log are not correctly rounded #47277

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Jan 15, 2018
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doc: show that f32::log and f64::log are not correctly rounded #47277

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0eba4c2
doc: show that `f32::log` and `f64::log` are not correctly rounded
tspiteri Jan 8, 2018
6d82e78
remove implementation detail from doc
tspiteri Jan 9, 2018
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17 changes: 8 additions & 9 deletions src/libstd/f32.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -472,20 +472,19 @@ impl f32 {

/// Returns the logarithm of the number with respect to an arbitrary base.
///
/// The result may not be correctly rounded owing to implementation details;
/// `self.log2()` can produce more accurate results for base 2, and
/// `self.log10()` can produce more accurate results for base 10.
///
/// ```
/// use std::f32;
///
/// let ten = 10.0f32;
/// let two = 2.0f32;
///
/// // log10(10) - 1 == 0
/// let abs_difference_10 = (ten.log(10.0) - 1.0).abs();
/// let five = 5.0f32;
///
/// // log2(2) - 1 == 0
/// let abs_difference_2 = (two.log(2.0) - 1.0).abs();
/// // log5(5) - 1 == 0
/// let abs_difference = (five.log(5.0) - 1.0).abs();
///
/// assert!(abs_difference_10 <= f32::EPSILON);
/// assert!(abs_difference_2 <= f32::EPSILON);
/// assert!(abs_difference <= f32::EPSILON);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
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17 changes: 8 additions & 9 deletions src/libstd/f64.rs
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Expand Up @@ -432,18 +432,17 @@ impl f64 {

/// Returns the logarithm of the number with respect to an arbitrary base.
///
/// ```
/// let ten = 10.0_f64;
/// let two = 2.0_f64;
/// The result may not be correctly rounded owing to implementation details;
/// `self.log2()` can produce more accurate results for base 2, and
/// `self.log10()` can produce more accurate results for base 10.
///
/// // log10(10) - 1 == 0
/// let abs_difference_10 = (ten.log(10.0) - 1.0).abs();
/// ```
/// let five = 5.0_f64;
///
/// // log2(2) - 1 == 0
/// let abs_difference_2 = (two.log(2.0) - 1.0).abs();
/// // log5(5) - 1 == 0
/// let abs_difference = (five.log(5.0) - 1.0).abs();
///
/// assert!(abs_difference_10 < 1e-10);
/// assert!(abs_difference_2 < 1e-10);
/// assert!(abs_difference < 1e-10);
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
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