| //! Constants for the `f64` double-precision floating point type. |
| //! |
| //! *[See also the `f64` primitive type][f64].* |
| //! |
| //! Mathematically significant numbers are provided in the `consts` sub-module. |
| //! |
| //! For the constants defined directly in this module |
| //! (as distinct from those defined in the `consts` sub-module), |
| //! new code should instead use the associated constants |
| //! defined directly on the `f64` type. |
| |
| #![stable(feature = "rust1", since = "1.0.0")] |
| |
| use crate::convert::FloatToInt; |
| #[cfg(not(test))] |
| use crate::intrinsics; |
| use crate::mem; |
| use crate::num::FpCategory; |
| |
| /// The radix or base of the internal representation of `f64`. |
| /// Use [`f64::RADIX`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let r = std::f64::RADIX; |
| /// |
| /// // intended way |
| /// let r = f64::RADIX; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `RADIX` associated constant on `f64`")] |
| pub const RADIX: u32 = f64::RADIX; |
| |
| /// Number of significant digits in base 2. |
| /// Use [`f64::MANTISSA_DIGITS`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let d = std::f64::MANTISSA_DIGITS; |
| /// |
| /// // intended way |
| /// let d = f64::MANTISSA_DIGITS; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated( |
| since = "TBD", |
| note = "replaced by the `MANTISSA_DIGITS` associated constant on `f64`" |
| )] |
| pub const MANTISSA_DIGITS: u32 = f64::MANTISSA_DIGITS; |
| |
| /// Approximate number of significant digits in base 10. |
| /// Use [`f64::DIGITS`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let d = std::f64::DIGITS; |
| /// |
| /// // intended way |
| /// let d = f64::DIGITS; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `DIGITS` associated constant on `f64`")] |
| pub const DIGITS: u32 = f64::DIGITS; |
| |
| /// [Machine epsilon] value for `f64`. |
| /// Use [`f64::EPSILON`] instead. |
| /// |
| /// This is the difference between `1.0` and the next larger representable number. |
| /// |
| /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let e = std::f64::EPSILON; |
| /// |
| /// // intended way |
| /// let e = f64::EPSILON; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `EPSILON` associated constant on `f64`")] |
| pub const EPSILON: f64 = f64::EPSILON; |
| |
| /// Smallest finite `f64` value. |
| /// Use [`f64::MIN`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let min = std::f64::MIN; |
| /// |
| /// // intended way |
| /// let min = f64::MIN; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MIN` associated constant on `f64`")] |
| pub const MIN: f64 = f64::MIN; |
| |
| /// Smallest positive normal `f64` value. |
| /// Use [`f64::MIN_POSITIVE`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let min = std::f64::MIN_POSITIVE; |
| /// |
| /// // intended way |
| /// let min = f64::MIN_POSITIVE; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MIN_POSITIVE` associated constant on `f64`")] |
| pub const MIN_POSITIVE: f64 = f64::MIN_POSITIVE; |
| |
| /// Largest finite `f64` value. |
| /// Use [`f64::MAX`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let max = std::f64::MAX; |
| /// |
| /// // intended way |
| /// let max = f64::MAX; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MAX` associated constant on `f64`")] |
| pub const MAX: f64 = f64::MAX; |
| |
| /// One greater than the minimum possible normal power of 2 exponent. |
| /// Use [`f64::MIN_EXP`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let min = std::f64::MIN_EXP; |
| /// |
| /// // intended way |
| /// let min = f64::MIN_EXP; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MIN_EXP` associated constant on `f64`")] |
| pub const MIN_EXP: i32 = f64::MIN_EXP; |
| |
| /// Maximum possible power of 2 exponent. |
| /// Use [`f64::MAX_EXP`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let max = std::f64::MAX_EXP; |
| /// |
| /// // intended way |
| /// let max = f64::MAX_EXP; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MAX_EXP` associated constant on `f64`")] |
| pub const MAX_EXP: i32 = f64::MAX_EXP; |
| |
| /// Minimum possible normal power of 10 exponent. |
| /// Use [`f64::MIN_10_EXP`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let min = std::f64::MIN_10_EXP; |
| /// |
| /// // intended way |
| /// let min = f64::MIN_10_EXP; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MIN_10_EXP` associated constant on `f64`")] |
| pub const MIN_10_EXP: i32 = f64::MIN_10_EXP; |
| |
| /// Maximum possible power of 10 exponent. |
| /// Use [`f64::MAX_10_EXP`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let max = std::f64::MAX_10_EXP; |
| /// |
| /// // intended way |
| /// let max = f64::MAX_10_EXP; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `MAX_10_EXP` associated constant on `f64`")] |
| pub const MAX_10_EXP: i32 = f64::MAX_10_EXP; |
| |
| /// Not a Number (NaN). |
| /// Use [`f64::NAN`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let nan = std::f64::NAN; |
| /// |
| /// // intended way |
| /// let nan = f64::NAN; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `NAN` associated constant on `f64`")] |
| pub const NAN: f64 = f64::NAN; |
| |
| /// Infinity (∞). |
| /// Use [`f64::INFINITY`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let inf = std::f64::INFINITY; |
| /// |
| /// // intended way |
| /// let inf = f64::INFINITY; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `INFINITY` associated constant on `f64`")] |
| pub const INFINITY: f64 = f64::INFINITY; |
| |
| /// Negative infinity (−∞). |
| /// Use [`f64::NEG_INFINITY`] instead. |
| /// |
| /// # Examples |
| /// |
| /// ```rust |
| /// // deprecated way |
| /// # #[allow(deprecated, deprecated_in_future)] |
| /// let ninf = std::f64::NEG_INFINITY; |
| /// |
| /// // intended way |
| /// let ninf = f64::NEG_INFINITY; |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "TBD", note = "replaced by the `NEG_INFINITY` associated constant on `f64`")] |
| pub const NEG_INFINITY: f64 = f64::NEG_INFINITY; |
| |
| /// Basic mathematical constants. |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub mod consts { |
| // FIXME: replace with mathematical constants from cmath. |
| |
| /// Archimedes' constant (π) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const PI: f64 = 3.14159265358979323846264338327950288_f64; |
| |
| /// The full circle constant (τ) |
| /// |
| /// Equal to 2π. |
| #[stable(feature = "tau_constant", since = "1.47.0")] |
| pub const TAU: f64 = 6.28318530717958647692528676655900577_f64; |
| |
| /// π/2 |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_PI_2: f64 = 1.57079632679489661923132169163975144_f64; |
| |
| /// π/3 |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_PI_3: f64 = 1.04719755119659774615421446109316763_f64; |
| |
| /// π/4 |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_PI_4: f64 = 0.785398163397448309615660845819875721_f64; |
| |
| /// π/6 |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_PI_6: f64 = 0.52359877559829887307710723054658381_f64; |
| |
| /// π/8 |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_PI_8: f64 = 0.39269908169872415480783042290993786_f64; |
| |
| /// 1/π |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_1_PI: f64 = 0.318309886183790671537767526745028724_f64; |
| |
| /// 2/π |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_2_PI: f64 = 0.636619772367581343075535053490057448_f64; |
| |
| /// 2/sqrt(π) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_2_SQRT_PI: f64 = 1.12837916709551257389615890312154517_f64; |
| |
| /// sqrt(2) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const SQRT_2: f64 = 1.41421356237309504880168872420969808_f64; |
| |
| /// 1/sqrt(2) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const FRAC_1_SQRT_2: f64 = 0.707106781186547524400844362104849039_f64; |
| |
| /// Euler's number (e) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const E: f64 = 2.71828182845904523536028747135266250_f64; |
| |
| /// log<sub>2</sub>(10) |
| #[stable(feature = "extra_log_consts", since = "1.43.0")] |
| pub const LOG2_10: f64 = 3.32192809488736234787031942948939018_f64; |
| |
| /// log<sub>2</sub>(e) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const LOG2_E: f64 = 1.44269504088896340735992468100189214_f64; |
| |
| /// log<sub>10</sub>(2) |
| #[stable(feature = "extra_log_consts", since = "1.43.0")] |
| pub const LOG10_2: f64 = 0.301029995663981195213738894724493027_f64; |
| |
| /// log<sub>10</sub>(e) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const LOG10_E: f64 = 0.434294481903251827651128918916605082_f64; |
| |
| /// ln(2) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const LN_2: f64 = 0.693147180559945309417232121458176568_f64; |
| |
| /// ln(10) |
| #[stable(feature = "rust1", since = "1.0.0")] |
| pub const LN_10: f64 = 2.30258509299404568401799145468436421_f64; |
| } |
| |
| #[cfg(not(test))] |
| impl f64 { |
| /// The radix or base of the internal representation of `f64`. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const RADIX: u32 = 2; |
| |
| /// Number of significant digits in base 2. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MANTISSA_DIGITS: u32 = 53; |
| /// Approximate number of significant digits in base 10. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const DIGITS: u32 = 15; |
| |
| /// [Machine epsilon] value for `f64`. |
| /// |
| /// This is the difference between `1.0` and the next larger representable number. |
| /// |
| /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const EPSILON: f64 = 2.2204460492503131e-16_f64; |
| |
| /// Smallest finite `f64` value. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MIN: f64 = -1.7976931348623157e+308_f64; |
| /// Smallest positive normal `f64` value. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MIN_POSITIVE: f64 = 2.2250738585072014e-308_f64; |
| /// Largest finite `f64` value. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MAX: f64 = 1.7976931348623157e+308_f64; |
| |
| /// One greater than the minimum possible normal power of 2 exponent. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MIN_EXP: i32 = -1021; |
| /// Maximum possible power of 2 exponent. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MAX_EXP: i32 = 1024; |
| |
| /// Minimum possible normal power of 10 exponent. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MIN_10_EXP: i32 = -307; |
| /// Maximum possible power of 10 exponent. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const MAX_10_EXP: i32 = 308; |
| |
| /// Not a Number (NaN). |
| /// |
| /// Note that IEEE 754 doesn't define just a single NaN value; |
| /// a plethora of bit patterns are considered to be NaN. |
| /// Furthermore, the standard makes a difference |
| /// between a "signaling" and a "quiet" NaN, |
| /// and allows inspecting its "payload" (the unspecified bits in the bit pattern). |
| /// This constant isn't guaranteed to equal to any specific NaN bitpattern, |
| /// and the stability of its representation over Rust versions |
| /// and target platforms isn't guaranteed. |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const NAN: f64 = 0.0_f64 / 0.0_f64; |
| /// Infinity (∞). |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const INFINITY: f64 = 1.0_f64 / 0.0_f64; |
| /// Negative infinity (−∞). |
| #[stable(feature = "assoc_int_consts", since = "1.43.0")] |
| pub const NEG_INFINITY: f64 = -1.0_f64 / 0.0_f64; |
| |
| /// Returns `true` if this value is NaN. |
| /// |
| /// ``` |
| /// let nan = f64::NAN; |
| /// let f = 7.0_f64; |
| /// |
| /// assert!(nan.is_nan()); |
| /// assert!(!f.is_nan()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_nan(self) -> bool { |
| self != self |
| } |
| |
| // FIXME(#50145): `abs` is publicly unavailable in libcore due to |
| // concerns about portability, so this implementation is for |
| // private use internally. |
| #[inline] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| pub(crate) const fn abs_private(self) -> f64 { |
| // SAFETY: This transmutation is fine. Probably. For the reasons std is using it. |
| unsafe { |
| mem::transmute::<u64, f64>(mem::transmute::<f64, u64>(self) & 0x7fff_ffff_ffff_ffff) |
| } |
| } |
| |
| /// Returns `true` if this value is positive infinity or negative infinity, and |
| /// `false` otherwise. |
| /// |
| /// ``` |
| /// let f = 7.0f64; |
| /// let inf = f64::INFINITY; |
| /// let neg_inf = f64::NEG_INFINITY; |
| /// let nan = f64::NAN; |
| /// |
| /// assert!(!f.is_infinite()); |
| /// assert!(!nan.is_infinite()); |
| /// |
| /// assert!(inf.is_infinite()); |
| /// assert!(neg_inf.is_infinite()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_infinite(self) -> bool { |
| // Getting clever with transmutation can result in incorrect answers on some FPUs |
| // FIXME: alter the Rust <-> Rust calling convention to prevent this problem. |
| // See https://github.com/rust-lang/rust/issues/72327 |
| (self == f64::INFINITY) | (self == f64::NEG_INFINITY) |
| } |
| |
| /// Returns `true` if this number is neither infinite nor NaN. |
| /// |
| /// ``` |
| /// let f = 7.0f64; |
| /// let inf: f64 = f64::INFINITY; |
| /// let neg_inf: f64 = f64::NEG_INFINITY; |
| /// let nan: f64 = f64::NAN; |
| /// |
| /// assert!(f.is_finite()); |
| /// |
| /// assert!(!nan.is_finite()); |
| /// assert!(!inf.is_finite()); |
| /// assert!(!neg_inf.is_finite()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_finite(self) -> bool { |
| // There's no need to handle NaN separately: if self is NaN, |
| // the comparison is not true, exactly as desired. |
| self.abs_private() < Self::INFINITY |
| } |
| |
| /// Returns `true` if the number is [subnormal]. |
| /// |
| /// ``` |
| /// let min = f64::MIN_POSITIVE; // 2.2250738585072014e-308_f64 |
| /// let max = f64::MAX; |
| /// let lower_than_min = 1.0e-308_f64; |
| /// let zero = 0.0_f64; |
| /// |
| /// assert!(!min.is_subnormal()); |
| /// assert!(!max.is_subnormal()); |
| /// |
| /// assert!(!zero.is_subnormal()); |
| /// assert!(!f64::NAN.is_subnormal()); |
| /// assert!(!f64::INFINITY.is_subnormal()); |
| /// // Values between `0` and `min` are Subnormal. |
| /// assert!(lower_than_min.is_subnormal()); |
| /// ``` |
| /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number |
| #[must_use] |
| #[stable(feature = "is_subnormal", since = "1.53.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_subnormal(self) -> bool { |
| matches!(self.classify(), FpCategory::Subnormal) |
| } |
| |
| /// Returns `true` if the number is neither zero, infinite, |
| /// [subnormal], or NaN. |
| /// |
| /// ``` |
| /// let min = f64::MIN_POSITIVE; // 2.2250738585072014e-308f64 |
| /// let max = f64::MAX; |
| /// let lower_than_min = 1.0e-308_f64; |
| /// let zero = 0.0f64; |
| /// |
| /// assert!(min.is_normal()); |
| /// assert!(max.is_normal()); |
| /// |
| /// assert!(!zero.is_normal()); |
| /// assert!(!f64::NAN.is_normal()); |
| /// assert!(!f64::INFINITY.is_normal()); |
| /// // Values between `0` and `min` are Subnormal. |
| /// assert!(!lower_than_min.is_normal()); |
| /// ``` |
| /// [subnormal]: https://en.wikipedia.org/wiki/Denormal_number |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_normal(self) -> bool { |
| matches!(self.classify(), FpCategory::Normal) |
| } |
| |
| /// Returns the floating point category of the number. If only one property |
| /// is going to be tested, it is generally faster to use the specific |
| /// predicate instead. |
| /// |
| /// ``` |
| /// use std::num::FpCategory; |
| /// |
| /// let num = 12.4_f64; |
| /// let inf = f64::INFINITY; |
| /// |
| /// assert_eq!(num.classify(), FpCategory::Normal); |
| /// assert_eq!(inf.classify(), FpCategory::Infinite); |
| /// ``` |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| pub const fn classify(self) -> FpCategory { |
| // A previous implementation tried to only use bitmask-based checks, |
| // using f64::to_bits to transmute the float to its bit repr and match on that. |
| // Unfortunately, floating point numbers can be much worse than that. |
| // This also needs to not result in recursive evaluations of f64::to_bits. |
| // |
| // On some processors, in some cases, LLVM will "helpfully" lower floating point ops, |
| // in spite of a request for them using f32 and f64, to things like x87 operations. |
| // These have an f64's mantissa, but can have a larger than normal exponent. |
| // FIXME(jubilee): Using x87 operations is never necessary in order to function |
| // on x86 processors for Rust-to-Rust calls, so this issue should not happen. |
| // Code generation should be adjusted to use non-C calling conventions, avoiding this. |
| // |
| // Thus, a value may compare unequal to infinity, despite having a "full" exponent mask. |
| // And it may not be NaN, as it can simply be an "overextended" finite value. |
| if self.is_nan() { |
| FpCategory::Nan |
| } else { |
| // However, std can't simply compare to zero to check for zero, either, |
| // as correctness requires avoiding equality tests that may be Subnormal == -0.0 |
| // because it may be wrong under "denormals are zero" and "flush to zero" modes. |
| // Most of std's targets don't use those, but they are used for thumbv7neon. |
| // So, this does use bitpattern matching for the rest. |
| |
| // SAFETY: f64 to u64 is fine. Usually. |
| // If control flow has gotten this far, the value is definitely in one of the categories |
| // that f64::partial_classify can correctly analyze. |
| unsafe { f64::partial_classify(self) } |
| } |
| } |
| |
| // This doesn't actually return a right answer for NaN on purpose, |
| // seeing as how it cannot correctly discern between a floating point NaN, |
| // and some normal floating point numbers truncated from an x87 FPU. |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| const unsafe fn partial_classify(self) -> FpCategory { |
| const EXP_MASK: u64 = 0x7ff0000000000000; |
| const MAN_MASK: u64 = 0x000fffffffffffff; |
| |
| // SAFETY: The caller is not asking questions for which this will tell lies. |
| let b = unsafe { mem::transmute::<f64, u64>(self) }; |
| match (b & MAN_MASK, b & EXP_MASK) { |
| (0, EXP_MASK) => FpCategory::Infinite, |
| (0, 0) => FpCategory::Zero, |
| (_, 0) => FpCategory::Subnormal, |
| _ => FpCategory::Normal, |
| } |
| } |
| |
| // This operates on bits, and only bits, so it can ignore concerns about weird FPUs. |
| // FIXME(jubilee): In a just world, this would be the entire impl for classify, |
| // plus a transmute. We do not live in a just world, but we can make it more so. |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| const fn classify_bits(b: u64) -> FpCategory { |
| const EXP_MASK: u64 = 0x7ff0000000000000; |
| const MAN_MASK: u64 = 0x000fffffffffffff; |
| |
| match (b & MAN_MASK, b & EXP_MASK) { |
| (0, EXP_MASK) => FpCategory::Infinite, |
| (_, EXP_MASK) => FpCategory::Nan, |
| (0, 0) => FpCategory::Zero, |
| (_, 0) => FpCategory::Subnormal, |
| _ => FpCategory::Normal, |
| } |
| } |
| |
| /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with |
| /// positive sign bit and positive infinity. Note that IEEE 754 doesn't assign any |
| /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that |
| /// the bit pattern of NaNs are conserved over arithmetic operations, the result of |
| /// `is_sign_positive` on a NaN might produce an unexpected result in some cases. |
| /// See [explanation of NaN as a special value](f32) for more info. |
| /// |
| /// ``` |
| /// let f = 7.0_f64; |
| /// let g = -7.0_f64; |
| /// |
| /// assert!(f.is_sign_positive()); |
| /// assert!(!g.is_sign_positive()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_sign_positive(self) -> bool { |
| !self.is_sign_negative() |
| } |
| |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "1.0.0", note = "renamed to is_sign_positive")] |
| #[inline] |
| #[doc(hidden)] |
| pub fn is_positive(self) -> bool { |
| self.is_sign_positive() |
| } |
| |
| /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with |
| /// negative sign bit and negative infinity. Note that IEEE 754 doesn't assign any |
| /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that |
| /// the bit pattern of NaNs are conserved over arithmetic operations, the result of |
| /// `is_sign_negative` on a NaN might produce an unexpected result in some cases. |
| /// See [explanation of NaN as a special value](f32) for more info. |
| /// |
| /// ``` |
| /// let f = 7.0_f64; |
| /// let g = -7.0_f64; |
| /// |
| /// assert!(!f.is_sign_negative()); |
| /// assert!(g.is_sign_negative()); |
| /// ``` |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[rustc_const_unstable(feature = "const_float_classify", issue = "72505")] |
| #[inline] |
| pub const fn is_sign_negative(self) -> bool { |
| // IEEE754 says: isSignMinus(x) is true if and only if x has negative sign. isSignMinus |
| // applies to zeros and NaNs as well. |
| // SAFETY: This is just transmuting to get the sign bit, it's fine. |
| unsafe { mem::transmute::<f64, u64>(self) & 0x8000_0000_0000_0000 != 0 } |
| } |
| |
| #[must_use] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[deprecated(since = "1.0.0", note = "renamed to is_sign_negative")] |
| #[inline] |
| #[doc(hidden)] |
| pub fn is_negative(self) -> bool { |
| self.is_sign_negative() |
| } |
| |
| /// Returns the least number greater than `self`. |
| /// |
| /// Let `TINY` be the smallest representable positive `f64`. Then, |
| /// - if `self.is_nan()`, this returns `self`; |
| /// - if `self` is [`NEG_INFINITY`], this returns [`MIN`]; |
| /// - if `self` is `-TINY`, this returns -0.0; |
| /// - if `self` is -0.0 or +0.0, this returns `TINY`; |
| /// - if `self` is [`MAX`] or [`INFINITY`], this returns [`INFINITY`]; |
| /// - otherwise the unique least value greater than `self` is returned. |
| /// |
| /// The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x` |
| /// is finite `x == x.next_up().next_down()` also holds. |
| /// |
| /// ```rust |
| /// #![feature(float_next_up_down)] |
| /// // f64::EPSILON is the difference between 1.0 and the next number up. |
| /// assert_eq!(1.0f64.next_up(), 1.0 + f64::EPSILON); |
| /// // But not for most numbers. |
| /// assert!(0.1f64.next_up() < 0.1 + f64::EPSILON); |
| /// assert_eq!(9007199254740992f64.next_up(), 9007199254740994.0); |
| /// ``` |
| /// |
| /// [`NEG_INFINITY`]: Self::NEG_INFINITY |
| /// [`INFINITY`]: Self::INFINITY |
| /// [`MIN`]: Self::MIN |
| /// [`MAX`]: Self::MAX |
| #[unstable(feature = "float_next_up_down", issue = "91399")] |
| #[rustc_const_unstable(feature = "float_next_up_down", issue = "91399")] |
| pub const fn next_up(self) -> Self { |
| // We must use strictly integer arithmetic to prevent denormals from |
| // flushing to zero after an arithmetic operation on some platforms. |
| const TINY_BITS: u64 = 0x1; // Smallest positive f64. |
| const CLEAR_SIGN_MASK: u64 = 0x7fff_ffff_ffff_ffff; |
| |
| let bits = self.to_bits(); |
| if self.is_nan() || bits == Self::INFINITY.to_bits() { |
| return self; |
| } |
| |
| let abs = bits & CLEAR_SIGN_MASK; |
| let next_bits = if abs == 0 { |
| TINY_BITS |
| } else if bits == abs { |
| bits + 1 |
| } else { |
| bits - 1 |
| }; |
| Self::from_bits(next_bits) |
| } |
| |
| /// Returns the greatest number less than `self`. |
| /// |
| /// Let `TINY` be the smallest representable positive `f64`. Then, |
| /// - if `self.is_nan()`, this returns `self`; |
| /// - if `self` is [`INFINITY`], this returns [`MAX`]; |
| /// - if `self` is `TINY`, this returns 0.0; |
| /// - if `self` is -0.0 or +0.0, this returns `-TINY`; |
| /// - if `self` is [`MIN`] or [`NEG_INFINITY`], this returns [`NEG_INFINITY`]; |
| /// - otherwise the unique greatest value less than `self` is returned. |
| /// |
| /// The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x` |
| /// is finite `x == x.next_down().next_up()` also holds. |
| /// |
| /// ```rust |
| /// #![feature(float_next_up_down)] |
| /// let x = 1.0f64; |
| /// // Clamp value into range [0, 1). |
| /// let clamped = x.clamp(0.0, 1.0f64.next_down()); |
| /// assert!(clamped < 1.0); |
| /// assert_eq!(clamped.next_up(), 1.0); |
| /// ``` |
| /// |
| /// [`NEG_INFINITY`]: Self::NEG_INFINITY |
| /// [`INFINITY`]: Self::INFINITY |
| /// [`MIN`]: Self::MIN |
| /// [`MAX`]: Self::MAX |
| #[unstable(feature = "float_next_up_down", issue = "91399")] |
| #[rustc_const_unstable(feature = "float_next_up_down", issue = "91399")] |
| pub const fn next_down(self) -> Self { |
| // We must use strictly integer arithmetic to prevent denormals from |
| // flushing to zero after an arithmetic operation on some platforms. |
| const NEG_TINY_BITS: u64 = 0x8000_0000_0000_0001; // Smallest (in magnitude) negative f64. |
| const CLEAR_SIGN_MASK: u64 = 0x7fff_ffff_ffff_ffff; |
| |
| let bits = self.to_bits(); |
| if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() { |
| return self; |
| } |
| |
| let abs = bits & CLEAR_SIGN_MASK; |
| let next_bits = if abs == 0 { |
| NEG_TINY_BITS |
| } else if bits == abs { |
| bits - 1 |
| } else { |
| bits + 1 |
| }; |
| Self::from_bits(next_bits) |
| } |
| |
| /// Takes the reciprocal (inverse) of a number, `1/x`. |
| /// |
| /// ``` |
| /// let x = 2.0_f64; |
| /// let abs_difference = (x.recip() - (1.0 / x)).abs(); |
| /// |
| /// assert!(abs_difference < 1e-10); |
| /// ``` |
| #[must_use = "this returns the result of the operation, without modifying the original"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn recip(self) -> f64 { |
| 1.0 / self |
| } |
| |
| /// Converts radians to degrees. |
| /// |
| /// ``` |
| /// let angle = std::f64::consts::PI; |
| /// |
| /// let abs_difference = (angle.to_degrees() - 180.0).abs(); |
| /// |
| /// assert!(abs_difference < 1e-10); |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub 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) |
| } |
| |
| /// Converts degrees to radians. |
| /// |
| /// ``` |
| /// let angle = 180.0_f64; |
| /// |
| /// let abs_difference = (angle.to_radians() - std::f64::consts::PI).abs(); |
| /// |
| /// assert!(abs_difference < 1e-10); |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn to_radians(self) -> f64 { |
| let value: f64 = consts::PI; |
| self * (value / 180.0) |
| } |
| |
| /// Returns the maximum of the two numbers, ignoring NaN. |
| /// |
| /// If one of the arguments is NaN, then the other argument is returned. |
| /// This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs; |
| /// this function handles all NaNs the same way and avoids maxNum's problems with associativity. |
| /// This also matches the behavior of libm’s fmax. |
| /// |
| /// ``` |
| /// let x = 1.0_f64; |
| /// let y = 2.0_f64; |
| /// |
| /// assert_eq!(x.max(y), y); |
| /// ``` |
| #[must_use = "this returns the result of the comparison, without modifying either input"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn max(self, other: f64) -> f64 { |
| intrinsics::maxnumf64(self, other) |
| } |
| |
| /// Returns the minimum of the two numbers, ignoring NaN. |
| /// |
| /// If one of the arguments is NaN, then the other argument is returned. |
| /// This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs; |
| /// this function handles all NaNs the same way and avoids minNum's problems with associativity. |
| /// This also matches the behavior of libm’s fmin. |
| /// |
| /// ``` |
| /// let x = 1.0_f64; |
| /// let y = 2.0_f64; |
| /// |
| /// assert_eq!(x.min(y), x); |
| /// ``` |
| #[must_use = "this returns the result of the comparison, without modifying either input"] |
| #[stable(feature = "rust1", since = "1.0.0")] |
| #[inline] |
| pub fn min(self, other: f64) -> f64 { |
| intrinsics::minnumf64(self, other) |
| } |
| |
| /// Returns the maximum of the two numbers, propagating NaN. |
| /// |
| /// This returns NaN when *either* argument is NaN, as opposed to |
| /// [`f64::max`] which only returns NaN when *both* arguments are NaN. |
| /// |
| /// ``` |
| /// #![feature(float_minimum_maximum)] |
| /// let x = 1.0_f64; |
| /// let y = 2.0_f64; |
| /// |
| /// assert_eq!(x.maximum(y), y); |
| /// assert!(x.maximum(f64::NAN).is_nan()); |
| /// ``` |
| /// |
| /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater |
| /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0. |
| /// Note that this follows the semantics specified in IEEE 754-2019. |
| /// |
| /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN |
| /// operand is conserved; see [explanation of NaN as a special value](f32) for more info. |
| #[must_use = "this returns the result of the comparison, without modifying either input"] |
| #[unstable(feature = "float_minimum_maximum", issue = "91079")] |
| #[inline] |
| pub fn maximum(self, other: f64) -> f64 { |
| if self > other { |
| self |
| } else if other > self { |
| other |
| } else if self == other { |
| if self.is_sign_positive() && other.is_sign_negative() { self } else { other } |
| } else { |
| self + other |
| } |
| } |
| |
| /// Returns the minimum of the two numbers, propagating NaN. |
| /// |
| /// This returns NaN when *either* argument is NaN, as opposed to |
| /// [`f64::min`] which only returns NaN when *both* arguments are NaN. |
| /// |
| /// ``` |
| /// #![feature(float_minimum_maximum)] |
| /// let x = 1.0_f64; |
| /// let y = 2.0_f64; |
| /// |
| /// assert_eq!(x.minimum(y), x); |
| /// assert!(x.minimum(f64::NAN).is_nan()); |
| /// ``` |
| /// |
| /// If one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser |
| /// of the two numbers. For this operation, -0.0 is considered to be less than +0.0. |
| /// Note that this follows the semantics specified in IEEE 754-2019. |
| /// |
| /// Also note that "propagation" of NaNs here doesn't necessarily mean that the bitpattern of a NaN |
| /// operand is conserved; see [explanation of NaN as a special value](f32) for more info. |
| #[must_use = "this returns the result of the comparison, without modifying either input"] |
| #[unstable(feature = "float_minimum_maximum", issue = "91079")] |
| #[inline] |
| pub fn minimum(self, other: f64) -> f64 { |
| if self < other { |
| self |
| } else if other < self { |
| other |
| } else if self == other { |
| if self.is_sign_negative() && other.is_sign_positive() { self } else { other } |
| } else { |
| self + other |
| } |
| } |
| |
| /// Rounds toward zero and converts to any primitive integer type, |
| /// assuming that the value is finite and fits in that type. |
| /// |
| /// ``` |
| /// let value = 4.6_f64; |
| /// let rounded = unsafe { value.to_int_unchecked::<u16>() }; |
| /// assert_eq!(rounded, 4); |
| /// |
| /// let value = -128.9_f64; |
| /// let rounded = unsafe { value.to_int_unchecked::<i8>() }; |
| /// assert_eq!(rounded, i8::MIN); |
| /// ``` |
| /// |
| /// # Safety |
| /// |
| /// The value must: |
| /// |
| /// * Not be `NaN` |
| /// * Not be infinite |
| /// * Be representable in the return type `Int`, after truncating off its fractional part |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "float_approx_unchecked_to", since = "1.44.0")] |
| #[inline] |
| pub unsafe fn to_int_unchecked<Int>(self) -> Int |
| where |
| Self: FloatToInt<Int>, |
| { |
| // SAFETY: the caller must uphold the safety contract for |
| // `FloatToInt::to_int_unchecked`. |
| unsafe { FloatToInt::<Int>::to_int_unchecked(self) } |
| } |
| |
| /// Raw transmutation to `u64`. |
| /// |
| /// This is currently identical to `transmute::<f64, u64>(self)` on all platforms. |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// Note that this function is distinct from `as` casting, which attempts to |
| /// preserve the *numeric* value, and not the bitwise value. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// assert!((1f64).to_bits() != 1f64 as u64); // to_bits() is not casting! |
| /// assert_eq!((12.5f64).to_bits(), 0x4029000000000000); |
| /// |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "float_bits_conv", since = "1.20.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[inline] |
| pub const fn to_bits(self) -> u64 { |
| // SAFETY: `u64` is a plain old datatype so we can always transmute to it. |
| // ...sorta. |
| // |
| // See the SAFETY comment in f64::from_bits for more. |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| const fn ct_f64_to_u64(ct: f64) -> u64 { |
| match ct.classify() { |
| FpCategory::Nan => { |
| panic!("const-eval error: cannot use f64::to_bits on a NaN") |
| } |
| FpCategory::Subnormal => { |
| panic!("const-eval error: cannot use f64::to_bits on a subnormal number") |
| } |
| FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => { |
| // SAFETY: We have a normal floating point number. Now we transmute, i.e. do a bitcopy. |
| unsafe { mem::transmute::<f64, u64>(ct) } |
| } |
| } |
| } |
| |
| #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 |
| fn rt_f64_to_u64(rt: f64) -> u64 { |
| // SAFETY: `u64` is a plain old datatype so we can always... uh... |
| // ...look, just pretend you forgot what you just read. |
| // Stability concerns. |
| unsafe { mem::transmute::<f64, u64>(rt) } |
| } |
| // SAFETY: We use internal implementations that either always work or fail at compile time. |
| unsafe { intrinsics::const_eval_select((self,), ct_f64_to_u64, rt_f64_to_u64) } |
| } |
| |
| /// Raw transmutation from `u64`. |
| /// |
| /// This is currently identical to `transmute::<u64, f64>(v)` on all platforms. |
| /// It turns out this is incredibly portable, for two reasons: |
| /// |
| /// * Floats and Ints have the same endianness on all supported platforms. |
| /// * IEEE 754 very precisely specifies the bit layout of floats. |
| /// |
| /// However there is one caveat: prior to the 2008 version of IEEE 754, how |
| /// to interpret the NaN signaling bit wasn't actually specified. Most platforms |
| /// (notably x86 and ARM) picked the interpretation that was ultimately |
| /// standardized in 2008, but some didn't (notably MIPS). As a result, all |
| /// signaling NaNs on MIPS are quiet NaNs on x86, and vice-versa. |
| /// |
| /// Rather than trying to preserve signaling-ness cross-platform, this |
| /// implementation favors preserving the exact bits. This means that |
| /// any payloads encoded in NaNs will be preserved even if the result of |
| /// this method is sent over the network from an x86 machine to a MIPS one. |
| /// |
| /// If the results of this method are only manipulated by the same |
| /// architecture that produced them, then there is no portability concern. |
| /// |
| /// If the input isn't NaN, then there is no portability concern. |
| /// |
| /// If you don't care about signaling-ness (very likely), then there is no |
| /// portability concern. |
| /// |
| /// Note that this function is distinct from `as` casting, which attempts to |
| /// preserve the *numeric* value, and not the bitwise value. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let v = f64::from_bits(0x4029000000000000); |
| /// assert_eq!(v, 12.5); |
| /// ``` |
| #[stable(feature = "float_bits_conv", since = "1.20.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[must_use] |
| #[inline] |
| pub const fn from_bits(v: u64) -> Self { |
| // It turns out the safety issues with sNaN were overblown! Hooray! |
| // SAFETY: `u64` is a plain old datatype so we can always transmute from it |
| // ...sorta. |
| // |
| // It turns out that at runtime, it is possible for a floating point number |
| // to be subject to floating point modes that alter nonzero subnormal numbers |
| // to zero on reads and writes, aka "denormals are zero" and "flush to zero". |
| // This is not a problem usually, but at least one tier2 platform for Rust |
| // actually exhibits an FTZ behavior by default: thumbv7neon |
| // aka "the Neon FPU in AArch32 state" |
| // |
| // Even with this, not all instructions exhibit the FTZ behaviors on thumbv7neon, |
| // so this should load the same bits if LLVM emits the "correct" instructions, |
| // but LLVM sometimes makes interesting choices about float optimization, |
| // and other FPUs may do similar. Thus, it is wise to indulge luxuriously in caution. |
| // |
| // In addition, on x86 targets with SSE or SSE2 disabled and the x87 FPU enabled, |
| // i.e. not soft-float, the way Rust does parameter passing can actually alter |
| // a number that is "not infinity" to have the same exponent as infinity, |
| // in a slightly unpredictable manner. |
| // |
| // And, of course evaluating to a NaN value is fairly nondeterministic. |
| // More precisely: when NaN should be returned is knowable, but which NaN? |
| // So far that's defined by a combination of LLVM and the CPU, not Rust. |
| // This function, however, allows observing the bitstring of a NaN, |
| // thus introspection on CTFE. |
| // |
| // In order to preserve, at least for the moment, const-to-runtime equivalence, |
| // reject any of these possible situations from happening. |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| const fn ct_u64_to_f64(ct: u64) -> f64 { |
| match f64::classify_bits(ct) { |
| FpCategory::Subnormal => { |
| panic!("const-eval error: cannot use f64::from_bits on a subnormal number") |
| } |
| FpCategory::Nan => { |
| panic!("const-eval error: cannot use f64::from_bits on NaN") |
| } |
| FpCategory::Infinite | FpCategory::Normal | FpCategory::Zero => { |
| // SAFETY: It's not a frumious number |
| unsafe { mem::transmute::<u64, f64>(ct) } |
| } |
| } |
| } |
| |
| #[inline(always)] // See https://github.com/rust-lang/compiler-builtins/issues/491 |
| fn rt_u64_to_f64(rt: u64) -> f64 { |
| // SAFETY: `u64` is a plain old datatype so we can always... uh... |
| // ...look, just pretend you forgot what you just read. |
| // Stability concerns. |
| unsafe { mem::transmute::<u64, f64>(rt) } |
| } |
| // SAFETY: We use internal implementations that either always work or fail at compile time. |
| unsafe { intrinsics::const_eval_select((v,), ct_u64_to_f64, rt_u64_to_f64) } |
| } |
| |
| /// Return the memory representation of this floating point number as a byte array in |
| /// big-endian (network) byte order. |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let bytes = 12.5f64.to_be_bytes(); |
| /// assert_eq!(bytes, [0x40, 0x29, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]); |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[inline] |
| pub const fn to_be_bytes(self) -> [u8; 8] { |
| self.to_bits().to_be_bytes() |
| } |
| |
| /// Return the memory representation of this floating point number as a byte array in |
| /// little-endian byte order. |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let bytes = 12.5f64.to_le_bytes(); |
| /// assert_eq!(bytes, [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x29, 0x40]); |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[inline] |
| pub const fn to_le_bytes(self) -> [u8; 8] { |
| self.to_bits().to_le_bytes() |
| } |
| |
| /// Return the memory representation of this floating point number as a byte array in |
| /// native byte order. |
| /// |
| /// As the target platform's native endianness is used, portable code |
| /// should use [`to_be_bytes`] or [`to_le_bytes`], as appropriate, instead. |
| /// |
| /// [`to_be_bytes`]: f64::to_be_bytes |
| /// [`to_le_bytes`]: f64::to_le_bytes |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let bytes = 12.5f64.to_ne_bytes(); |
| /// assert_eq!( |
| /// bytes, |
| /// if cfg!(target_endian = "big") { |
| /// [0x40, 0x29, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00] |
| /// } else { |
| /// [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x29, 0x40] |
| /// } |
| /// ); |
| /// ``` |
| #[must_use = "this returns the result of the operation, \ |
| without modifying the original"] |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[inline] |
| pub const fn to_ne_bytes(self) -> [u8; 8] { |
| self.to_bits().to_ne_bytes() |
| } |
| |
| /// Create a floating point value from its representation as a byte array in big endian. |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let value = f64::from_be_bytes([0x40, 0x29, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]); |
| /// assert_eq!(value, 12.5); |
| /// ``` |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[must_use] |
| #[inline] |
| pub const fn from_be_bytes(bytes: [u8; 8]) -> Self { |
| Self::from_bits(u64::from_be_bytes(bytes)) |
| } |
| |
| /// Create a floating point value from its representation as a byte array in little endian. |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let value = f64::from_le_bytes([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x29, 0x40]); |
| /// assert_eq!(value, 12.5); |
| /// ``` |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[must_use] |
| #[inline] |
| pub const fn from_le_bytes(bytes: [u8; 8]) -> Self { |
| Self::from_bits(u64::from_le_bytes(bytes)) |
| } |
| |
| /// Create a floating point value from its representation as a byte array in native endian. |
| /// |
| /// As the target platform's native endianness is used, portable code |
| /// likely wants to use [`from_be_bytes`] or [`from_le_bytes`], as |
| /// appropriate instead. |
| /// |
| /// [`from_be_bytes`]: f64::from_be_bytes |
| /// [`from_le_bytes`]: f64::from_le_bytes |
| /// |
| /// See [`from_bits`](Self::from_bits) for some discussion of the |
| /// portability of this operation (there are almost no issues). |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// let value = f64::from_ne_bytes(if cfg!(target_endian = "big") { |
| /// [0x40, 0x29, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00] |
| /// } else { |
| /// [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x29, 0x40] |
| /// }); |
| /// assert_eq!(value, 12.5); |
| /// ``` |
| #[stable(feature = "float_to_from_bytes", since = "1.40.0")] |
| #[rustc_const_unstable(feature = "const_float_bits_conv", issue = "72447")] |
| #[must_use] |
| #[inline] |
| pub const fn from_ne_bytes(bytes: [u8; 8]) -> Self { |
| Self::from_bits(u64::from_ne_bytes(bytes)) |
| } |
| |
| /// Return the ordering between `self` and `other`. |
| /// |
| /// Unlike the standard partial comparison between floating point numbers, |
| /// this comparison always produces an ordering in accordance to |
| /// the `totalOrder` predicate as defined in the IEEE 754 (2008 revision) |
| /// floating point standard. The values are ordered in the following sequence: |
| /// |
| /// - negative quiet NaN |
| /// - negative signaling NaN |
| /// - negative infinity |
| /// - negative numbers |
| /// - negative subnormal numbers |
| /// - negative zero |
| /// - positive zero |
| /// - positive subnormal numbers |
| /// - positive numbers |
| /// - positive infinity |
| /// - positive signaling NaN |
| /// - positive quiet NaN. |
| /// |
| /// The ordering established by this function does not always agree with the |
| /// [`PartialOrd`] and [`PartialEq`] implementations of `f64`. For example, |
| /// they consider negative and positive zero equal, while `total_cmp` |
| /// doesn't. |
| /// |
| /// The interpretation of the signaling NaN bit follows the definition in |
| /// the IEEE 754 standard, which may not match the interpretation by some of |
| /// the older, non-conformant (e.g. MIPS) hardware implementations. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// struct GoodBoy { |
| /// name: String, |
| /// weight: f64, |
| /// } |
| /// |
| /// let mut bois = vec![ |
| /// GoodBoy { name: "Pucci".to_owned(), weight: 0.1 }, |
| /// GoodBoy { name: "Woofer".to_owned(), weight: 99.0 }, |
| /// GoodBoy { name: "Yapper".to_owned(), weight: 10.0 }, |
| /// GoodBoy { name: "Chonk".to_owned(), weight: f64::INFINITY }, |
| /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f64::NAN }, |
| /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 }, |
| /// ]; |
| /// |
| /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight)); |
| /// # assert!(bois.into_iter().map(|b| b.weight) |
| /// # .zip([-5.0, 0.1, 10.0, 99.0, f64::INFINITY, f64::NAN].iter()) |
| /// # .all(|(a, b)| a.to_bits() == b.to_bits())) |
| /// ``` |
| #[stable(feature = "total_cmp", since = "1.62.0")] |
| #[must_use] |
| #[inline] |
| pub fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering { |
| let mut left = self.to_bits() as i64; |
| let mut right = other.to_bits() as i64; |
| |
| // In case of negatives, flip all the bits except the sign |
| // to achieve a similar layout as two's complement integers |
| // |
| // Why does this work? IEEE 754 floats consist of three fields: |
| // Sign bit, exponent and mantissa. The set of exponent and mantissa |
| // fields as a whole have the property that their bitwise order is |
| // equal to the numeric magnitude where the magnitude is defined. |
| // The magnitude is not normally defined on NaN values, but |
| // IEEE 754 totalOrder defines the NaN values also to follow the |
| // bitwise order. This leads to order explained in the doc comment. |
| // However, the representation of magnitude is the same for negative |
| // and positive numbers – only the sign bit is different. |
| // To easily compare the floats as signed integers, we need to |
| // flip the exponent and mantissa bits in case of negative numbers. |
| // We effectively convert the numbers to "two's complement" form. |
| // |
| // To do the flipping, we construct a mask and XOR against it. |
| // We branchlessly calculate an "all-ones except for the sign bit" |
| // mask from negative-signed values: right shifting sign-extends |
| // the integer, so we "fill" the mask with sign bits, and then |
| // convert to unsigned to push one more zero bit. |
| // On positive values, the mask is all zeros, so it's a no-op. |
| left ^= (((left >> 63) as u64) >> 1) as i64; |
| right ^= (((right >> 63) as u64) >> 1) as i64; |
| |
| left.cmp(&right) |
| } |
| |
| /// Restrict a value to a certain interval unless it is NaN. |
| /// |
| /// Returns `max` if `self` is greater than `max`, and `min` if `self` is |
| /// less than `min`. Otherwise this returns `self`. |
| /// |
| /// Note that this function returns NaN if the initial value was NaN as |
| /// well. |
| /// |
| /// # Panics |
| /// |
| /// Panics if `min > max`, `min` is NaN, or `max` is NaN. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// assert!((-3.0f64).clamp(-2.0, 1.0) == -2.0); |
| /// assert!((0.0f64).clamp(-2.0, 1.0) == 0.0); |
| /// assert!((2.0f64).clamp(-2.0, 1.0) == 1.0); |
| /// assert!((f64::NAN).clamp(-2.0, 1.0).is_nan()); |
| /// ``` |
| #[must_use = "method returns a new number and does not mutate the original value"] |
| #[stable(feature = "clamp", since = "1.50.0")] |
| #[inline] |
| pub fn clamp(mut self, min: f64, max: f64) -> f64 { |
| assert!(min <= max); |
| if self < min { |
| self = min; |
| } |
| if self > max { |
| self = max; |
| } |
| self |
| } |
| } |