//! Constants for the `f32` single-precision floating point type. //! //! *[See also the `f32` primitive type][f32].* //! //! 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 `f32` type. #![stable(feature = "rust1", since = "1.0.0")] use crate::convert::FloatToInt; use crate::num::FpCategory; use crate::panic::const_assert; use crate::{cfg_select, intrinsics, mem}; /// The radix or base of the internal representation of `f32`. /// Use [`f32::RADIX`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let r = std::f32::RADIX; /// /// // intended way /// let r = f32::RADIX; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `RADIX` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_radix"] pub const RADIX: u32 = f32::RADIX; /// Number of significant digits in base 2. /// Use [`f32::MANTISSA_DIGITS`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let d = std::f32::MANTISSA_DIGITS; /// /// // intended way /// let d = f32::MANTISSA_DIGITS; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated( since = "TBD", note = "replaced by the `MANTISSA_DIGITS` associated constant on `f32`" )] #[rustc_diagnostic_item = "f32_legacy_const_mantissa_dig"] pub const MANTISSA_DIGITS: u32 = f32::MANTISSA_DIGITS; /// Approximate number of significant digits in base 10. /// Use [`f32::DIGITS`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let d = std::f32::DIGITS; /// /// // intended way /// let d = f32::DIGITS; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `DIGITS` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_digits"] pub const DIGITS: u32 = f32::DIGITS; /// [Machine epsilon] value for `f32`. /// Use [`f32::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::f32::EPSILON; /// /// // intended way /// let e = f32::EPSILON; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `EPSILON` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_epsilon"] pub const EPSILON: f32 = f32::EPSILON; /// Smallest finite `f32` value. /// Use [`f32::MIN`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let min = std::f32::MIN; /// /// // intended way /// let min = f32::MIN; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MIN` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_min"] pub const MIN: f32 = f32::MIN; /// Smallest positive normal `f32` value. /// Use [`f32::MIN_POSITIVE`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let min = std::f32::MIN_POSITIVE; /// /// // intended way /// let min = f32::MIN_POSITIVE; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MIN_POSITIVE` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_min_positive"] pub const MIN_POSITIVE: f32 = f32::MIN_POSITIVE; /// Largest finite `f32` value. /// Use [`f32::MAX`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let max = std::f32::MAX; /// /// // intended way /// let max = f32::MAX; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MAX` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_max"] pub const MAX: f32 = f32::MAX; /// One greater than the minimum possible normal power of 2 exponent. /// Use [`f32::MIN_EXP`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let min = std::f32::MIN_EXP; /// /// // intended way /// let min = f32::MIN_EXP; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MIN_EXP` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_min_exp"] pub const MIN_EXP: i32 = f32::MIN_EXP; /// Maximum possible power of 2 exponent. /// Use [`f32::MAX_EXP`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let max = std::f32::MAX_EXP; /// /// // intended way /// let max = f32::MAX_EXP; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MAX_EXP` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_max_exp"] pub const MAX_EXP: i32 = f32::MAX_EXP; /// Minimum possible normal power of 10 exponent. /// Use [`f32::MIN_10_EXP`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let min = std::f32::MIN_10_EXP; /// /// // intended way /// let min = f32::MIN_10_EXP; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MIN_10_EXP` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_min_10_exp"] pub const MIN_10_EXP: i32 = f32::MIN_10_EXP; /// Maximum possible power of 10 exponent. /// Use [`f32::MAX_10_EXP`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let max = std::f32::MAX_10_EXP; /// /// // intended way /// let max = f32::MAX_10_EXP; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `MAX_10_EXP` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_max_10_exp"] pub const MAX_10_EXP: i32 = f32::MAX_10_EXP; /// Not a Number (NaN). /// Use [`f32::NAN`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let nan = std::f32::NAN; /// /// // intended way /// let nan = f32::NAN; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `NAN` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_nan"] pub const NAN: f32 = f32::NAN; /// Infinity (∞). /// Use [`f32::INFINITY`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let inf = std::f32::INFINITY; /// /// // intended way /// let inf = f32::INFINITY; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `INFINITY` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_infinity"] pub const INFINITY: f32 = f32::INFINITY; /// Negative infinity (−∞). /// Use [`f32::NEG_INFINITY`] instead. /// /// # Examples /// /// ```rust /// // deprecated way /// # #[allow(deprecated, deprecated_in_future)] /// let ninf = std::f32::NEG_INFINITY; /// /// // intended way /// let ninf = f32::NEG_INFINITY; /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[deprecated(since = "TBD", note = "replaced by the `NEG_INFINITY` associated constant on `f32`")] #[rustc_diagnostic_item = "f32_legacy_const_neg_infinity"] pub const NEG_INFINITY: f32 = f32::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: f32 = 3.14159265358979323846264338327950288_f32; /// The full circle constant (τ) /// /// Equal to 2π. #[stable(feature = "tau_constant", since = "1.47.0")] pub const TAU: f32 = 6.28318530717958647692528676655900577_f32; /// The golden ratio (φ) #[unstable(feature = "more_float_constants", issue = "146939")] pub const PHI: f32 = 1.618033988749894848204586834365638118_f32; /// The Euler-Mascheroni constant (γ) #[unstable(feature = "more_float_constants", issue = "146939")] pub const EGAMMA: f32 = 0.577215664901532860606512090082402431_f32; /// π/2 #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_PI_2: f32 = 1.57079632679489661923132169163975144_f32; /// π/3 #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_PI_3: f32 = 1.04719755119659774615421446109316763_f32; /// π/4 #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_PI_4: f32 = 0.785398163397448309615660845819875721_f32; /// π/6 #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_PI_6: f32 = 0.52359877559829887307710723054658381_f32; /// π/8 #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_PI_8: f32 = 0.39269908169872415480783042290993786_f32; /// 1/π #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_1_PI: f32 = 0.318309886183790671537767526745028724_f32; /// 1/sqrt(π) #[unstable(feature = "more_float_constants", issue = "146939")] pub const FRAC_1_SQRT_PI: f32 = 0.564189583547756286948079451560772586_f32; /// 1/sqrt(2π) #[doc(alias = "FRAC_1_SQRT_TAU")] #[unstable(feature = "more_float_constants", issue = "146939")] pub const FRAC_1_SQRT_2PI: f32 = 0.398942280401432677939946059934381868_f32; /// 2/π #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_2_PI: f32 = 0.636619772367581343075535053490057448_f32; /// 2/sqrt(π) #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_2_SQRT_PI: f32 = 1.12837916709551257389615890312154517_f32; /// sqrt(2) #[stable(feature = "rust1", since = "1.0.0")] pub const SQRT_2: f32 = 1.41421356237309504880168872420969808_f32; /// 1/sqrt(2) #[stable(feature = "rust1", since = "1.0.0")] pub const FRAC_1_SQRT_2: f32 = 0.707106781186547524400844362104849039_f32; /// sqrt(3) #[unstable(feature = "more_float_constants", issue = "146939")] pub const SQRT_3: f32 = 1.732050807568877293527446341505872367_f32; /// 1/sqrt(3) #[unstable(feature = "more_float_constants", issue = "146939")] pub const FRAC_1_SQRT_3: f32 = 0.577350269189625764509148780501957456_f32; /// Euler's number (e) #[stable(feature = "rust1", since = "1.0.0")] pub const E: f32 = 2.71828182845904523536028747135266250_f32; /// log2(e) #[stable(feature = "rust1", since = "1.0.0")] pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32; /// log2(10) #[stable(feature = "extra_log_consts", since = "1.43.0")] pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32; /// log10(e) #[stable(feature = "rust1", since = "1.0.0")] pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32; /// log10(2) #[stable(feature = "extra_log_consts", since = "1.43.0")] pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32; /// ln(2) #[stable(feature = "rust1", since = "1.0.0")] pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32; /// ln(10) #[stable(feature = "rust1", since = "1.0.0")] pub const LN_10: f32 = 2.30258509299404568401799145468436421_f32; } impl f32 { /// The radix or base of the internal representation of `f32`. #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const RADIX: u32 = 2; /// Number of significant digits in base 2. /// /// Note that the size of the mantissa in the bitwise representation is one /// smaller than this since the leading 1 is not stored explicitly. #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MANTISSA_DIGITS: u32 = 24; /// Approximate number of significant digits in base 10. /// /// This is the maximum x such that any decimal number with x /// significant digits can be converted to `f32` and back without loss. /// /// Equal to floor(log10 2[`MANTISSA_DIGITS`] − 1). /// /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const DIGITS: u32 = 6; /// [Machine epsilon] value for `f32`. /// /// This is the difference between `1.0` and the next larger representable number. /// /// Equal to 21 − [`MANTISSA_DIGITS`]. /// /// [Machine epsilon]: https://en.wikipedia.org/wiki/Machine_epsilon /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS #[stable(feature = "assoc_int_consts", since = "1.43.0")] #[rustc_diagnostic_item = "f32_epsilon"] pub const EPSILON: f32 = 1.19209290e-07_f32; /// Smallest finite `f32` value. /// /// Equal to −[`MAX`]. /// /// [`MAX`]: f32::MAX #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MIN: f32 = -3.40282347e+38_f32; /// Smallest positive normal `f32` value. /// /// Equal to 2[`MIN_EXP`] − 1. /// /// [`MIN_EXP`]: f32::MIN_EXP #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MIN_POSITIVE: f32 = 1.17549435e-38_f32; /// Largest finite `f32` value. /// /// Equal to /// (1 − 2−[`MANTISSA_DIGITS`]) 2[`MAX_EXP`]. /// /// [`MANTISSA_DIGITS`]: f32::MANTISSA_DIGITS /// [`MAX_EXP`]: f32::MAX_EXP #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MAX: f32 = 3.40282347e+38_f32; /// One greater than the minimum possible *normal* power of 2 exponent /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition). /// /// This corresponds to the exact minimum possible *normal* power of 2 exponent /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition). /// In other words, all normal numbers representable by this type are /// greater than or equal to 0.5 × 2MIN_EXP. #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MIN_EXP: i32 = -125; /// One greater than the maximum possible power of 2 exponent /// for a significand bounded by 1 ≤ x < 2 (i.e. the IEEE definition). /// /// This corresponds to the exact maximum possible power of 2 exponent /// for a significand bounded by 0.5 ≤ x < 1 (i.e. the C definition). /// In other words, all numbers representable by this type are /// strictly less than 2MAX_EXP. #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MAX_EXP: i32 = 128; /// Minimum x for which 10x is normal. /// /// Equal to ceil(log10 [`MIN_POSITIVE`]). /// /// [`MIN_POSITIVE`]: f32::MIN_POSITIVE #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MIN_10_EXP: i32 = -37; /// Maximum x for which 10x is normal. /// /// Equal to floor(log10 [`MAX`]). /// /// [`MAX`]: f32::MAX #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const MAX_10_EXP: i32 = 38; /// 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) /// and its sign. See the [specification of NaN bit patterns](f32#nan-bit-patterns) for more /// info. /// /// This constant is guaranteed to be a quiet NaN (on targets that follow the Rust assumptions /// that the quiet/signaling bit being set to 1 indicates a quiet NaN). Beyond that, nothing is /// guaranteed about the specific bit pattern chosen here: both payload and sign are arbitrary. /// The concrete bit pattern may change across Rust versions and target platforms. #[stable(feature = "assoc_int_consts", since = "1.43.0")] #[rustc_diagnostic_item = "f32_nan"] #[allow(clippy::eq_op)] pub const NAN: f32 = 0.0_f32 / 0.0_f32; /// Infinity (∞). #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const INFINITY: f32 = 1.0_f32 / 0.0_f32; /// Negative infinity (−∞). #[stable(feature = "assoc_int_consts", since = "1.43.0")] pub const NEG_INFINITY: f32 = -1.0_f32 / 0.0_f32; /// Sign bit pub(crate) const SIGN_MASK: u32 = 0x8000_0000; /// Exponent mask pub(crate) const EXP_MASK: u32 = 0x7f80_0000; /// Mantissa mask pub(crate) const MAN_MASK: u32 = 0x007f_ffff; /// Minimum representable positive value (min subnormal) const TINY_BITS: u32 = 0x1; /// Minimum representable negative value (min negative subnormal) const NEG_TINY_BITS: u32 = Self::TINY_BITS | Self::SIGN_MASK; /// Returns `true` if this value is NaN. /// /// ``` /// let nan = f32::NAN; /// let f = 7.0_f32; /// /// assert!(nan.is_nan()); /// assert!(!f.is_nan()); /// ``` #[must_use] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")] #[inline] #[allow(clippy::eq_op)] // > if you intended to check if the operand is NaN, use `.is_nan()` instead :) pub const fn is_nan(self) -> bool { self != self } /// Returns `true` if this value is positive infinity or negative infinity, and /// `false` otherwise. /// /// ``` /// let f = 7.0f32; /// let inf = f32::INFINITY; /// let neg_inf = f32::NEG_INFINITY; /// let nan = f32::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_stable(feature = "const_float_classify", since = "1.83.0")] #[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 == f32::INFINITY) | (self == f32::NEG_INFINITY) } /// Returns `true` if this number is neither infinite nor NaN. /// /// ``` /// let f = 7.0f32; /// let inf = f32::INFINITY; /// let neg_inf = f32::NEG_INFINITY; /// let nan = f32::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_stable(feature = "const_float_classify", since = "1.83.0")] #[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() < Self::INFINITY } /// Returns `true` if the number is [subnormal]. /// /// ``` /// let min = f32::MIN_POSITIVE; // 1.17549435e-38f32 /// let max = f32::MAX; /// let lower_than_min = 1.0e-40_f32; /// let zero = 0.0_f32; /// /// assert!(!min.is_subnormal()); /// assert!(!max.is_subnormal()); /// /// assert!(!zero.is_subnormal()); /// assert!(!f32::NAN.is_subnormal()); /// assert!(!f32::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_stable(feature = "const_float_classify", since = "1.83.0")] #[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 = f32::MIN_POSITIVE; // 1.17549435e-38f32 /// let max = f32::MAX; /// let lower_than_min = 1.0e-40_f32; /// let zero = 0.0_f32; /// /// assert!(min.is_normal()); /// assert!(max.is_normal()); /// /// assert!(!zero.is_normal()); /// assert!(!f32::NAN.is_normal()); /// assert!(!f32::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_stable(feature = "const_float_classify", since = "1.83.0")] #[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_f32; /// let inf = f32::INFINITY; /// /// assert_eq!(num.classify(), FpCategory::Normal); /// assert_eq!(inf.classify(), FpCategory::Infinite); /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")] pub const fn classify(self) -> FpCategory { // We used to have complicated logic here that avoids the simple bit-based tests to work // around buggy codegen for x87 targets (see // https://github.com/rust-lang/rust/issues/114479). However, some LLVM versions later, none // of our tests is able to find any difference between the complicated and the naive // version, so now we are back to the naive version. let b = self.to_bits(); match (b & Self::MAN_MASK, b & Self::EXP_MASK) { (0, Self::EXP_MASK) => FpCategory::Infinite, (_, Self::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 or non-portable result. See the [specification /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == 1.0` /// if you need fully portable behavior (will return `false` for all NaNs). /// /// ``` /// let f = 7.0_f32; /// let g = -7.0_f32; /// /// assert!(f.is_sign_positive()); /// assert!(!g.is_sign_positive()); /// ``` #[must_use] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")] #[inline] pub const fn is_sign_positive(self) -> bool { !self.is_sign_negative() } /// 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 or non-portable result. See the [specification /// of NaN bit patterns](f32#nan-bit-patterns) for more info. Use `self.signum() == -1.0` /// if you need fully portable behavior (will return `false` for all NaNs). /// /// ``` /// let f = 7.0f32; /// let g = -7.0f32; /// /// assert!(!f.is_sign_negative()); /// assert!(g.is_sign_negative()); /// ``` #[must_use] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_classify", since = "1.83.0")] #[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. self.to_bits() & 0x8000_0000 != 0 } /// Returns the least number greater than `self`. /// /// Let `TINY` be the smallest representable positive `f32`. 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 /// // f32::EPSILON is the difference between 1.0 and the next number up. /// assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON); /// // But not for most numbers. /// assert!(0.1f32.next_up() < 0.1 + f32::EPSILON); /// assert_eq!(16777216f32.next_up(), 16777218.0); /// ``` /// /// This operation corresponds to IEEE-754 `nextUp`. /// /// [`NEG_INFINITY`]: Self::NEG_INFINITY /// [`INFINITY`]: Self::INFINITY /// [`MIN`]: Self::MIN /// [`MAX`]: Self::MAX #[inline] #[doc(alias = "nextUp")] #[stable(feature = "float_next_up_down", since = "1.86.0")] #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")] pub const fn next_up(self) -> Self { // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing // denormals to zero. This is in general unsound and unsupported, but here // we do our best to still produce the correct result on such targets. let bits = self.to_bits(); if self.is_nan() || bits == Self::INFINITY.to_bits() { return self; } let abs = bits & !Self::SIGN_MASK; let next_bits = if abs == 0 { Self::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 `f32`. 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 /// let x = 1.0f32; /// // Clamp value into range [0, 1). /// let clamped = x.clamp(0.0, 1.0f32.next_down()); /// assert!(clamped < 1.0); /// assert_eq!(clamped.next_up(), 1.0); /// ``` /// /// This operation corresponds to IEEE-754 `nextDown`. /// /// [`NEG_INFINITY`]: Self::NEG_INFINITY /// [`INFINITY`]: Self::INFINITY /// [`MIN`]: Self::MIN /// [`MAX`]: Self::MAX #[inline] #[doc(alias = "nextDown")] #[stable(feature = "float_next_up_down", since = "1.86.0")] #[rustc_const_stable(feature = "float_next_up_down", since = "1.86.0")] pub const fn next_down(self) -> Self { // Some targets violate Rust's assumption of IEEE semantics, e.g. by flushing // denormals to zero. This is in general unsound and unsupported, but here // we do our best to still produce the correct result on such targets. let bits = self.to_bits(); if self.is_nan() || bits == Self::NEG_INFINITY.to_bits() { return self; } let abs = bits & !Self::SIGN_MASK; let next_bits = if abs == 0 { Self::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_f32; /// let abs_difference = (x.recip() - (1.0 / x)).abs(); /// /// assert!(abs_difference <= f32::EPSILON); /// ``` #[must_use = "this returns the result of the operation, without modifying the original"] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn recip(self) -> f32 { 1.0 / self } /// Converts radians to degrees. /// /// # Unspecified precision /// /// The precision of this function is non-deterministic. This means it varies by platform, /// Rust version, and can even differ within the same execution from one invocation to the next. /// /// # Examples /// /// ``` /// let angle = std::f32::consts::PI; /// /// let abs_difference = (angle.to_degrees() - 180.0).abs(); /// # #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))] /// assert!(abs_difference <= f32::EPSILON); /// ``` #[must_use = "this returns the result of the operation, \ without modifying the original"] #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn to_degrees(self) -> f32 { // Use a literal to avoid double rounding, consts::PI is already rounded, // and dividing would round again. const PIS_IN_180: f32 = 57.2957795130823208767981548141051703_f32; self * PIS_IN_180 } /// Converts degrees to radians. /// /// # Unspecified precision /// /// The precision of this function is non-deterministic. This means it varies by platform, /// Rust version, and can even differ within the same execution from one invocation to the next. /// /// # Examples /// /// ``` /// let angle = 180.0f32; /// /// let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs(); /// /// assert!(abs_difference <= f32::EPSILON); /// ``` #[must_use = "this returns the result of the operation, \ without modifying the original"] #[stable(feature = "f32_deg_rad_conversions", since = "1.7.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn to_radians(self) -> f32 { // The division here is correctly rounded with respect to the true value of π/180. // Although π is irrational and already rounded, the double rounding happens // to produce correct result for f32. const RADS_PER_DEG: f32 = consts::PI / 180.0; self * RADS_PER_DEG } /// 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. In particular, if the inputs compare equal /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically. /// /// ``` /// let x = 1.0f32; /// let y = 2.0f32; /// /// 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")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn max(self, other: f32) -> f32 { intrinsics::maxnumf32(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. In particular, if the inputs compare equal /// (such as for the case of `+0.0` and `-0.0`), either input may be returned non-deterministically. /// /// ``` /// let x = 1.0f32; /// let y = 2.0f32; /// /// 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")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn min(self, other: f32) -> f32 { intrinsics::minnumf32(self, other) } /// Returns the maximum of the two numbers, propagating NaN. /// /// This returns NaN when *either* argument is NaN, as opposed to /// [`f32::max`] which only returns NaN when *both* arguments are NaN. /// /// ``` /// #![feature(float_minimum_maximum)] /// let x = 1.0f32; /// let y = 2.0f32; /// /// assert_eq!(x.maximum(y), y); /// assert!(x.maximum(f32::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 the [specification of NaN bit patterns](f32#nan-bit-patterns) 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 const fn maximum(self, other: f32) -> f32 { intrinsics::maximumf32(self, other) } /// Returns the minimum of the two numbers, propagating NaN. /// /// This returns NaN when *either* argument is NaN, as opposed to /// [`f32::min`] which only returns NaN when *both* arguments are NaN. /// /// ``` /// #![feature(float_minimum_maximum)] /// let x = 1.0f32; /// let y = 2.0f32; /// /// assert_eq!(x.minimum(y), x); /// assert!(x.minimum(f32::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 the [specification of NaN bit patterns](f32#nan-bit-patterns) 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 const fn minimum(self, other: f32) -> f32 { intrinsics::minimumf32(self, other) } /// Calculates the midpoint (average) between `self` and `rhs`. /// /// This returns NaN when *either* argument is NaN or if a combination of /// +inf and -inf is provided as arguments. /// /// # Examples /// /// ``` /// assert_eq!(1f32.midpoint(4.0), 2.5); /// assert_eq!((-5.5f32).midpoint(8.0), 1.25); /// ``` #[inline] #[doc(alias = "average")] #[stable(feature = "num_midpoint", since = "1.85.0")] #[rustc_const_stable(feature = "num_midpoint", since = "1.85.0")] pub const fn midpoint(self, other: f32) -> f32 { cfg_select! { // Allow faster implementation that have known good 64-bit float // implementations. Falling back to the branchy code on targets that don't // have 64-bit hardware floats or buggy implementations. // https://github.com/rust-lang/rust/pull/121062#issuecomment-2123408114 any( target_arch = "x86_64", target_arch = "aarch64", all(any(target_arch = "riscv32", target_arch = "riscv64"), target_feature = "d"), all(target_arch = "loongarch64", target_feature = "d"), all(target_arch = "arm", target_feature = "vfp2"), target_arch = "wasm32", target_arch = "wasm64", ) => { ((self as f64 + other as f64) / 2.0) as f32 } _ => { const HI: f32 = f32::MAX / 2.; let (a, b) = (self, other); let abs_a = a.abs(); let abs_b = b.abs(); if abs_a <= HI && abs_b <= HI { // Overflow is impossible (a + b) / 2. } else { (a / 2.) + (b / 2.) } } } } /// 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_f32; /// let rounded = unsafe { value.to_int_unchecked::() }; /// assert_eq!(rounded, 4); /// /// let value = -128.9_f32; /// let rounded = unsafe { value.to_int_unchecked::() }; /// 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(self) -> Int where Self: FloatToInt, { // SAFETY: the caller must uphold the safety contract for // `FloatToInt::to_int_unchecked`. unsafe { FloatToInt::::to_int_unchecked(self) } } /// Raw transmutation to `u32`. /// /// This is currently identical to `transmute::(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_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting! /// assert_eq!((12.5f32).to_bits(), 0x41480000); /// /// ``` #[must_use = "this returns the result of the operation, \ without modifying the original"] #[stable(feature = "float_bits_conv", since = "1.20.0")] #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[inline] #[allow(unnecessary_transmutes)] pub const fn to_bits(self) -> u32 { // SAFETY: `u32` is a plain old datatype so we can always transmute to it. unsafe { mem::transmute(self) } } /// Raw transmutation from `u32`. /// /// This is currently identical to `transmute::(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 signalingness (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 = f32::from_bits(0x41480000); /// assert_eq!(v, 12.5); /// ``` #[stable(feature = "float_bits_conv", since = "1.20.0")] #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[must_use] #[inline] #[allow(unnecessary_transmutes)] pub const fn from_bits(v: u32) -> Self { // It turns out the safety issues with sNaN were overblown! Hooray! // SAFETY: `u32` is a plain old datatype so we can always transmute from it. unsafe { mem::transmute(v) } } /// Returns 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 = 12.5f32.to_be_bytes(); /// assert_eq!(bytes, [0x41, 0x48, 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_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[inline] pub const fn to_be_bytes(self) -> [u8; 4] { self.to_bits().to_be_bytes() } /// Returns 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 = 12.5f32.to_le_bytes(); /// assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]); /// ``` #[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_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[inline] pub const fn to_le_bytes(self) -> [u8; 4] { self.to_bits().to_le_bytes() } /// Returns 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`]: f32::to_be_bytes /// [`to_le_bytes`]: f32::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 = 12.5f32.to_ne_bytes(); /// assert_eq!( /// bytes, /// if cfg!(target_endian = "big") { /// [0x41, 0x48, 0x00, 0x00] /// } else { /// [0x00, 0x00, 0x48, 0x41] /// } /// ); /// ``` #[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_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[inline] pub const fn to_ne_bytes(self) -> [u8; 4] { self.to_bits().to_ne_bytes() } /// Creates 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 = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]); /// assert_eq!(value, 12.5); /// ``` #[stable(feature = "float_to_from_bytes", since = "1.40.0")] #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[must_use] #[inline] pub const fn from_be_bytes(bytes: [u8; 4]) -> Self { Self::from_bits(u32::from_be_bytes(bytes)) } /// Creates 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 = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]); /// assert_eq!(value, 12.5); /// ``` #[stable(feature = "float_to_from_bytes", since = "1.40.0")] #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[must_use] #[inline] pub const fn from_le_bytes(bytes: [u8; 4]) -> Self { Self::from_bits(u32::from_le_bytes(bytes)) } /// Creates 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`]: f32::from_be_bytes /// [`from_le_bytes`]: f32::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 = f32::from_ne_bytes(if cfg!(target_endian = "big") { /// [0x41, 0x48, 0x00, 0x00] /// } else { /// [0x00, 0x00, 0x48, 0x41] /// }); /// assert_eq!(value, 12.5); /// ``` #[stable(feature = "float_to_from_bytes", since = "1.40.0")] #[rustc_const_stable(feature = "const_float_bits_conv", since = "1.83.0")] #[must_use] #[inline] pub const fn from_ne_bytes(bytes: [u8; 4]) -> Self { Self::from_bits(u32::from_ne_bytes(bytes)) } /// Returns 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 `f32`. 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: f32, /// } /// /// 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: f32::INFINITY }, /// GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN }, /// GoodBoy { name: "Floaty".to_owned(), weight: -5.0 }, /// ]; /// /// bois.sort_by(|a, b| a.weight.total_cmp(&b.weight)); /// /// // `f32::NAN` could be positive or negative, which will affect the sort order. /// if f32::NAN.is_sign_negative() { /// assert!(bois.into_iter().map(|b| b.weight) /// .zip([f32::NAN, -5.0, 0.1, 10.0, 99.0, f32::INFINITY].iter()) /// .all(|(a, b)| a.to_bits() == b.to_bits())) /// } else { /// assert!(bois.into_iter().map(|b| b.weight) /// .zip([-5.0, 0.1, 10.0, 99.0, f32::INFINITY, f32::NAN].iter()) /// .all(|(a, b)| a.to_bits() == b.to_bits())) /// } /// ``` #[stable(feature = "total_cmp", since = "1.62.0")] #[rustc_const_unstable(feature = "const_cmp", issue = "143800")] #[must_use] #[inline] pub const fn total_cmp(&self, other: &Self) -> crate::cmp::Ordering { let mut left = self.to_bits() as i32; let mut right = other.to_bits() as i32; // 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 >> 31) as u32) >> 1) as i32; right ^= (((right >> 31) as u32) >> 1) as i32; 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!((-3.0f32).clamp(-2.0, 1.0) == -2.0); /// assert!((0.0f32).clamp(-2.0, 1.0) == 0.0); /// assert!((2.0f32).clamp(-2.0, 1.0) == 1.0); /// assert!((f32::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")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn clamp(mut self, min: f32, max: f32) -> f32 { const_assert!( min <= max, "min > max, or either was NaN", "min > max, or either was NaN. min = {min:?}, max = {max:?}", min: f32, max: f32, ); if self < min { self = min; } if self > max { self = max; } self } /// Computes the absolute value of `self`. /// /// This function always returns the precise result. /// /// # Examples /// /// ``` /// let x = 3.5_f32; /// let y = -3.5_f32; /// /// assert_eq!(x.abs(), x); /// assert_eq!(y.abs(), -y); /// /// assert!(f32::NAN.abs().is_nan()); /// ``` #[must_use = "method returns a new number and does not mutate the original value"] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn abs(self) -> f32 { intrinsics::fabsf32(self) } /// Returns a number that represents the sign of `self`. /// /// - `1.0` if the number is positive, `+0.0` or `INFINITY` /// - `-1.0` if the number is negative, `-0.0` or `NEG_INFINITY` /// - NaN if the number is NaN /// /// # Examples /// /// ``` /// let f = 3.5_f32; /// /// assert_eq!(f.signum(), 1.0); /// assert_eq!(f32::NEG_INFINITY.signum(), -1.0); /// /// assert!(f32::NAN.signum().is_nan()); /// ``` #[must_use = "method returns a new number and does not mutate the original value"] #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] #[inline] pub const fn signum(self) -> f32 { if self.is_nan() { Self::NAN } else { 1.0_f32.copysign(self) } } /// Returns a number composed of the magnitude of `self` and the sign of /// `sign`. /// /// Equal to `self` if the sign of `self` and `sign` are the same, otherwise equal to `-self`. /// If `self` is a NaN, then a NaN with the same payload as `self` and the sign bit of `sign` is /// returned. /// /// If `sign` is a NaN, then this operation will still carry over its sign into the result. 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 `copysign` with `sign` being a NaN might produce an unexpected or non-portable /// result. See the [specification of NaN bit patterns](primitive@f32#nan-bit-patterns) for more /// info. /// /// # Examples /// /// ``` /// let f = 3.5_f32; /// /// assert_eq!(f.copysign(0.42), 3.5_f32); /// assert_eq!(f.copysign(-0.42), -3.5_f32); /// assert_eq!((-f).copysign(0.42), 3.5_f32); /// assert_eq!((-f).copysign(-0.42), -3.5_f32); /// /// assert!(f32::NAN.copysign(1.0).is_nan()); /// ``` #[must_use = "method returns a new number and does not mutate the original value"] #[inline] #[stable(feature = "copysign", since = "1.35.0")] #[rustc_const_stable(feature = "const_float_methods", since = "1.85.0")] pub const fn copysign(self, sign: f32) -> f32 { intrinsics::copysignf32(self, sign) } /// Float addition that allows optimizations based on algebraic rules. /// /// See [algebraic operators](primitive@f32#algebraic-operators) for more info. #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "float_algebraic", issue = "136469")] #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")] #[inline] pub const fn algebraic_add(self, rhs: f32) -> f32 { intrinsics::fadd_algebraic(self, rhs) } /// Float subtraction that allows optimizations based on algebraic rules. /// /// See [algebraic operators](primitive@f32#algebraic-operators) for more info. #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "float_algebraic", issue = "136469")] #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")] #[inline] pub const fn algebraic_sub(self, rhs: f32) -> f32 { intrinsics::fsub_algebraic(self, rhs) } /// Float multiplication that allows optimizations based on algebraic rules. /// /// See [algebraic operators](primitive@f32#algebraic-operators) for more info. #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "float_algebraic", issue = "136469")] #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")] #[inline] pub const fn algebraic_mul(self, rhs: f32) -> f32 { intrinsics::fmul_algebraic(self, rhs) } /// Float division that allows optimizations based on algebraic rules. /// /// See [algebraic operators](primitive@f32#algebraic-operators) for more info. #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "float_algebraic", issue = "136469")] #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")] #[inline] pub const fn algebraic_div(self, rhs: f32) -> f32 { intrinsics::fdiv_algebraic(self, rhs) } /// Float remainder that allows optimizations based on algebraic rules. /// /// See [algebraic operators](primitive@f32#algebraic-operators) for more info. #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "float_algebraic", issue = "136469")] #[rustc_const_unstable(feature = "float_algebraic", issue = "136469")] #[inline] pub const fn algebraic_rem(self, rhs: f32) -> f32 { intrinsics::frem_algebraic(self, rhs) } } /// Experimental implementations of floating point functions in `core`. /// /// _The standalone functions in this module are for testing only. /// They will be stabilized as inherent methods._ #[unstable(feature = "core_float_math", issue = "137578")] pub mod math { use crate::intrinsics; use crate::num::libm; /// Experimental version of `floor` in `core`. See [`f32::floor`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let f = 3.7_f32; /// let g = 3.0_f32; /// let h = -3.7_f32; /// /// assert_eq!(f32::math::floor(f), 3.0); /// assert_eq!(f32::math::floor(g), 3.0); /// assert_eq!(f32::math::floor(h), -4.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::floor`]: ../../../std/primitive.f32.html#method.floor #[inline] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub const fn floor(x: f32) -> f32 { intrinsics::floorf32(x) } /// Experimental version of `ceil` in `core`. See [`f32::ceil`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let f = 3.01_f32; /// let g = 4.0_f32; /// /// assert_eq!(f32::math::ceil(f), 4.0); /// assert_eq!(f32::math::ceil(g), 4.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::ceil`]: ../../../std/primitive.f32.html#method.ceil #[inline] #[doc(alias = "ceiling")] #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "core_float_math", issue = "137578")] pub const fn ceil(x: f32) -> f32 { intrinsics::ceilf32(x) } /// Experimental version of `round` in `core`. See [`f32::round`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let f = 3.3_f32; /// let g = -3.3_f32; /// let h = -3.7_f32; /// let i = 3.5_f32; /// let j = 4.5_f32; /// /// assert_eq!(f32::math::round(f), 3.0); /// assert_eq!(f32::math::round(g), -3.0); /// assert_eq!(f32::math::round(h), -4.0); /// assert_eq!(f32::math::round(i), 4.0); /// assert_eq!(f32::math::round(j), 5.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::round`]: ../../../std/primitive.f32.html#method.round #[inline] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub const fn round(x: f32) -> f32 { intrinsics::roundf32(x) } /// Experimental version of `round_ties_even` in `core`. See [`f32::round_ties_even`] for /// details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let f = 3.3_f32; /// let g = -3.3_f32; /// let h = 3.5_f32; /// let i = 4.5_f32; /// /// assert_eq!(f32::math::round_ties_even(f), 3.0); /// assert_eq!(f32::math::round_ties_even(g), -3.0); /// assert_eq!(f32::math::round_ties_even(h), 4.0); /// assert_eq!(f32::math::round_ties_even(i), 4.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::round_ties_even`]: ../../../std/primitive.f32.html#method.round_ties_even #[inline] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub const fn round_ties_even(x: f32) -> f32 { intrinsics::round_ties_even_f32(x) } /// Experimental version of `trunc` in `core`. See [`f32::trunc`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let f = 3.7_f32; /// let g = 3.0_f32; /// let h = -3.7_f32; /// /// assert_eq!(f32::math::trunc(f), 3.0); /// assert_eq!(f32::math::trunc(g), 3.0); /// assert_eq!(f32::math::trunc(h), -3.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::trunc`]: ../../../std/primitive.f32.html#method.trunc #[inline] #[doc(alias = "truncate")] #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "core_float_math", issue = "137578")] pub const fn trunc(x: f32) -> f32 { intrinsics::truncf32(x) } /// Experimental version of `fract` in `core`. See [`f32::fract`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let x = 3.6_f32; /// let y = -3.6_f32; /// let abs_difference_x = (f32::math::fract(x) - 0.6).abs(); /// let abs_difference_y = (f32::math::fract(y) - (-0.6)).abs(); /// /// assert!(abs_difference_x <= f32::EPSILON); /// assert!(abs_difference_y <= f32::EPSILON); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::fract`]: ../../../std/primitive.f32.html#method.fract #[inline] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub const fn fract(x: f32) -> f32 { x - trunc(x) } /// Experimental version of `mul_add` in `core`. See [`f32::mul_add`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// # // FIXME(#140515): mingw has an incorrect fma /// # // https://sourceforge.net/p/mingw-w64/bugs/848/ /// # #[cfg(all(target_os = "windows", target_env = "gnu", not(target_abi = "llvm")))] { /// use core::f32; /// /// let m = 10.0_f32; /// let x = 4.0_f32; /// let b = 60.0_f32; /// /// assert_eq!(f32::math::mul_add(m, x, b), 100.0); /// assert_eq!(m * x + b, 100.0); /// /// 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!( /// f32::math::mul_add(one_plus_eps, 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); /// # } /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::mul_add`]: ../../../std/primitive.f32.html#method.mul_add #[inline] #[doc(alias = "fmaf", alias = "fusedMultiplyAdd")] #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "core_float_math", issue = "137578")] #[rustc_const_unstable(feature = "const_mul_add", issue = "146724")] pub const fn mul_add(x: f32, y: f32, z: f32) -> f32 { intrinsics::fmaf32(x, y, z) } /// Experimental version of `div_euclid` in `core`. See [`f32::div_euclid`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let a: f32 = 7.0; /// let b = 4.0; /// assert_eq!(f32::math::div_euclid(a, b), 1.0); // 7.0 > 4.0 * 1.0 /// assert_eq!(f32::math::div_euclid(-a, b), -2.0); // -7.0 >= 4.0 * -2.0 /// assert_eq!(f32::math::div_euclid(a, -b), -1.0); // 7.0 >= -4.0 * -1.0 /// assert_eq!(f32::math::div_euclid(-a, -b), 2.0); // -7.0 >= -4.0 * 2.0 /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::div_euclid`]: ../../../std/primitive.f32.html#method.div_euclid #[inline] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub fn div_euclid(x: f32, rhs: f32) -> f32 { let q = trunc(x / rhs); if x % rhs < 0.0 { return if rhs > 0.0 { q - 1.0 } else { q + 1.0 }; } q } /// Experimental version of `rem_euclid` in `core`. See [`f32::rem_euclid`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let a: f32 = 7.0; /// let b = 4.0; /// assert_eq!(f32::math::rem_euclid(a, b), 3.0); /// assert_eq!(f32::math::rem_euclid(-a, b), 1.0); /// assert_eq!(f32::math::rem_euclid(a, -b), 3.0); /// assert_eq!(f32::math::rem_euclid(-a, -b), 1.0); /// // limitation due to round-off error /// assert!(f32::math::rem_euclid(-f32::EPSILON, 3.0) != 0.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::rem_euclid`]: ../../../std/primitive.f32.html#method.rem_euclid #[inline] #[doc(alias = "modulo", alias = "mod")] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub fn rem_euclid(x: f32, rhs: f32) -> f32 { let r = x % rhs; if r < 0.0 { r + rhs.abs() } else { r } } /// Experimental version of `powi` in `core`. See [`f32::powi`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let x = 2.0_f32; /// let abs_difference = (f32::math::powi(x, 2) - (x * x)).abs(); /// assert!(abs_difference <= 1e-5); /// /// assert_eq!(f32::math::powi(f32::NAN, 0), 1.0); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::powi`]: ../../../std/primitive.f32.html#method.powi #[inline] #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "core_float_math", issue = "137578")] pub fn powi(x: f32, n: i32) -> f32 { intrinsics::powif32(x, n) } /// Experimental version of `sqrt` in `core`. See [`f32::sqrt`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let positive = 4.0_f32; /// let negative = -4.0_f32; /// let negative_zero = -0.0_f32; /// /// assert_eq!(f32::math::sqrt(positive), 2.0); /// assert!(f32::math::sqrt(negative).is_nan()); /// assert_eq!(f32::math::sqrt(negative_zero), negative_zero); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::sqrt`]: ../../../std/primitive.f32.html#method.sqrt #[inline] #[doc(alias = "squareRoot")] #[unstable(feature = "core_float_math", issue = "137578")] #[must_use = "method returns a new number and does not mutate the original value"] pub fn sqrt(x: f32) -> f32 { intrinsics::sqrtf32(x) } /// Experimental version of `abs_sub` in `core`. See [`f32::abs_sub`] for details. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let x = 3.0f32; /// let y = -3.0f32; /// /// let abs_difference_x = (f32::math::abs_sub(x, 1.0) - 2.0).abs(); /// let abs_difference_y = (f32::math::abs_sub(y, 1.0) - 0.0).abs(); /// /// assert!(abs_difference_x <= 1e-6); /// assert!(abs_difference_y <= 1e-6); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::abs_sub`]: ../../../std/primitive.f32.html#method.abs_sub #[inline] #[stable(feature = "rust1", since = "1.0.0")] #[deprecated( since = "1.10.0", note = "you probably meant `(self - other).abs()`: \ this operation is `(self - other).max(0.0)` \ except that `abs_sub` also propagates NaNs (also \ known as `fdimf` in C). If you truly need the positive \ difference, consider using that expression or the C function \ `fdimf`, depending on how you wish to handle NaN (please consider \ filing an issue describing your use-case too)." )] #[must_use = "method returns a new number and does not mutate the original value"] pub fn abs_sub(x: f32, other: f32) -> f32 { libm::fdimf(x, other) } /// Experimental version of `cbrt` in `core`. See [`f32::cbrt`] for details. /// /// # Unspecified precision /// /// The precision of this function is non-deterministic. This means it varies by platform, Rust version, and /// can even differ within the same execution from one invocation to the next. /// This function currently corresponds to the `cbrtf` from libc on Unix /// and Windows. Note that this might change in the future. /// /// # Examples /// /// ``` /// #![feature(core_float_math)] /// /// use core::f32; /// /// let x = 8.0f32; /// /// // x^(1/3) - 2 == 0 /// let abs_difference = (f32::math::cbrt(x) - 2.0).abs(); /// /// assert!(abs_difference <= 1e-6); /// ``` /// /// _This standalone function is for testing only. /// It will be stabilized as an inherent method._ /// /// [`f32::cbrt`]: ../../../std/primitive.f32.html#method.cbrt #[inline] #[must_use = "method returns a new number and does not mutate the original value"] #[unstable(feature = "core_float_math", issue = "137578")] pub fn cbrt(x: f32) -> f32 { libm::cbrtf(x) } }