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Use the guaranteed precision of a couple of float functions in docs #121861

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Mar 2, 2024
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Use the guaranteed precision of a couple of float functions in docs #121861

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24 changes: 13 additions & 11 deletions library/std/src/f32.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -186,11 +186,8 @@ impl f32 {
/// let x = 3.5_f32;
/// let y = -3.5_f32;
///
/// let abs_difference_x = (x.abs() - x).abs();
/// let abs_difference_y = (y.abs() - (-y)).abs();
///
/// assert!(abs_difference_x <= f32::EPSILON);
/// assert!(abs_difference_y <= f32::EPSILON);
/// assert_eq!(x.abs(), x);
/// assert_eq!(y.abs(), -y);
///
/// assert!(f32::NAN.abs().is_nan());
/// ```
Expand Down Expand Up @@ -276,10 +273,17 @@ impl f32 {
/// let x = 4.0_f32;
/// let b = 60.0_f32;
///
/// // 100.0
/// let abs_difference = (m.mul_add(x, b) - ((m * x) + b)).abs();
/// assert_eq!(m.mul_add(x, b), 100.0);
/// assert_eq!(m * x + b, 100.0);
///
/// assert!(abs_difference <= f32::EPSILON);
/// let one_plus_eps = 1.0_f32 + f32::EPSILON;
/// let one_minus_eps = 1.0_f32 - f32::EPSILON;
/// let minus_one = -1.0_f32;
///
/// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
/// assert_eq!(one_plus_eps.mul_add(one_minus_eps, minus_one), -f32::EPSILON * f32::EPSILON);
/// // Different rounding with the non-fused multiply and add.
/// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
/// ```
#[rustc_allow_incoherent_impl]
#[must_use = "method returns a new number and does not mutate the original value"]
Expand Down Expand Up @@ -426,9 +430,7 @@ impl f32 {
/// let negative = -4.0_f32;
/// let negative_zero = -0.0_f32;
///
/// let abs_difference = (positive.sqrt() - 2.0).abs();
///
/// assert!(abs_difference <= f32::EPSILON);
/// assert_eq!(positive.sqrt(), 2.0);
/// assert!(negative.sqrt().is_nan());
/// assert!(negative_zero.sqrt() == negative_zero);
/// ```
Expand Down
24 changes: 13 additions & 11 deletions library/std/src/f64.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -186,11 +186,8 @@ impl f64 {
/// let x = 3.5_f64;
/// let y = -3.5_f64;
///
/// let abs_difference_x = (x.abs() - x).abs();
/// let abs_difference_y = (y.abs() - (-y)).abs();
///
/// assert!(abs_difference_x < 1e-10);
/// assert!(abs_difference_y < 1e-10);
/// assert_eq!(x.abs(), x);
/// assert_eq!(y.abs(), -y);
///
/// assert!(f64::NAN.abs().is_nan());
/// ```
Expand Down Expand Up @@ -276,10 +273,17 @@ impl f64 {
/// let x = 4.0_f64;
/// let b = 60.0_f64;
///
/// // 100.0
/// let abs_difference = (m.mul_add(x, b) - ((m * x) + b)).abs();
/// assert_eq!(m.mul_add(x, b), 100.0);
/// assert_eq!(m * x + b, 100.0);
///
/// assert!(abs_difference < 1e-10);
/// let one_plus_eps = 1.0_f64 + f64::EPSILON;
/// let one_minus_eps = 1.0_f64 - f64::EPSILON;
/// let minus_one = -1.0_f64;
///
/// // The exact result (1 + eps) * (1 - eps) = 1 - eps * eps.
/// assert_eq!(one_plus_eps.mul_add(one_minus_eps, minus_one), -f64::EPSILON * f64::EPSILON);
/// // Different rounding with the non-fused multiply and add.
/// assert_eq!(one_plus_eps * one_minus_eps + minus_one, 0.0);
/// ```
#[rustc_allow_incoherent_impl]
#[must_use = "method returns a new number and does not mutate the original value"]
Expand Down Expand Up @@ -426,9 +430,7 @@ impl f64 {
/// let negative = -4.0_f64;
/// let negative_zero = -0.0_f64;
///
/// let abs_difference = (positive.sqrt() - 2.0).abs();
///
/// assert!(abs_difference < 1e-10);
/// assert_eq!(positive.sqrt(), 2.0);
/// assert!(negative.sqrt().is_nan());
/// assert!(negative_zero.sqrt() == negative_zero);
/// ```
Expand Down
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