Primitive Type f128

🔬This is a nightly-only experimental API. (f128 #116909)

A 128-bit floating-point type (specifically, the “binary128” type defined in IEEE 754-2008).

This type is very similar to f32 and f64, but has increased precision by using twice as many bits as f64. Please see the documentation for f32 or Wikipedia on quad-precision values for more information.

Note that no platforms have hardware support for f128 without enabling target specific features, as for all instruction set architectures f128 is considered an optional feature. Only Power ISA (“PowerPC”) and RISC-V specify it, and only certain microarchitectures actually implement it. For x86-64 and AArch64, ISA support is not even specified, so it will always be a software implementation significantly slower than f64.

Note: f128 support is incomplete. Many platforms will not be able to link math functions. On x86 in particular, these functions do link but their results are always incorrect.

See also the std::f128::consts module.

Implementations

impl f128

pub const RADIX: u32 = 2u32

🔬This is a nightly-only experimental API. (f128 #116909)

The radix or base of the internal representation of f128.

pub const MANTISSA_DIGITS: u32 = 113u32

🔬This is a nightly-only experimental API. (f128 #116909)

Number of significant digits in base 2.

pub const DIGITS: u32 = 33u32

🔬This is a nightly-only experimental API. (f128 #116909)

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 f128 and back without loss.

Equal to floor(log₁₀ 2^{MANTISSA_DIGITS − 1}).

pub const EPSILON: f128 = 1.92592994438723585305597794258492732E-34f128

🔬This is a nightly-only experimental API. (f128 #116909)

Machine epsilon value for f128.

This is the difference between 1.0 and the next larger representable number.

Equal to 2^{1 − MANTISSA_DIGITS}.

pub const MIN: f128 = -1.18973149535723176508575932662800702E+4932f128

🔬This is a nightly-only experimental API. (f128 #116909)

Smallest finite f128 value.

Equal to −MAX.

pub const MIN_POSITIVE: f128 = 3.3621031431120935062626778173217526E-4932f128

🔬This is a nightly-only experimental API. (f128 #116909)

Smallest positive normal f128 value.

Equal to 2^{MIN_EXP − 1}.

pub const MAX: f128 = 1.18973149535723176508575932662800702E+4932f128

🔬This is a nightly-only experimental API. (f128 #116909)

Largest finite f128 value.

Equal to (1 − 2^{−MANTISSA_DIGITS}) 2^MAX_EXP.

pub const MIN_EXP: i32 = -16_381i32

🔬This is a nightly-only experimental API. (f128 #116909)

One greater than the minimum possible normal power of 2 exponent.

If x = MIN_EXP, then normal numbers ≥ 0.5 × 2^x.

pub const MAX_EXP: i32 = 16_384i32

🔬This is a nightly-only experimental API. (f128 #116909)

Maximum possible power of 2 exponent.

If x = MAX_EXP, then normal numbers < 1 × 2^x.

pub const MIN_10_EXP: i32 = -4_931i32

🔬This is a nightly-only experimental API. (f128 #116909)

Minimum x for which 10^x is normal.

Equal to ceil(log₁₀ MIN_POSITIVE).

pub const MAX_10_EXP: i32 = 4_932i32

🔬This is a nightly-only experimental API. (f128 #116909)

Maximum x for which 10^x is normal.

Equal to floor(log₁₀ MAX).

pub const NAN: f128 = NaN_f128

🔬This is a nightly-only experimental API. (f128 #116909)

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.

pub const INFINITY: f128 = +Inf_f128

🔬This is a nightly-only experimental API. (f128 #116909)

Infinity (∞).

pub const NEG_INFINITY: f128 = -Inf_f128

🔬This is a nightly-only experimental API. (f128 #116909)

Negative infinity (−∞).

pub const fn is_nan(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

Returns true if this value is NaN.

#![feature(f128)]

let nan = f128::NAN;
let f = 7.0_f128;

assert!(nan.is_nan());
assert!(!f.is_nan());

pub const fn is_infinite(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

Returns true if this value is positive infinity or negative infinity, and false otherwise.

#![feature(f128)]

let f = 7.0f128;
let inf = f128::INFINITY;
let neg_inf = f128::NEG_INFINITY;
let nan = f128::NAN;

assert!(!f.is_infinite());
assert!(!nan.is_infinite());

assert!(inf.is_infinite());
assert!(neg_inf.is_infinite());

pub const fn is_finite(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

Returns true if this number is neither infinite nor NaN.

#![feature(f128)]

let f = 7.0f128;
let inf: f128 = f128::INFINITY;
let neg_inf: f128 = f128::NEG_INFINITY;
let nan: f128 = f128::NAN;

assert!(f.is_finite());

assert!(!nan.is_finite());
assert!(!inf.is_finite());
assert!(!neg_inf.is_finite());

pub const fn is_subnormal(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

Returns true if the number is subnormal.

#![feature(f128)]

let min = f128::MIN_POSITIVE; // 3.362103143e-4932f128
let max = f128::MAX;
let lower_than_min = 1.0e-4960_f128;
let zero = 0.0_f128;

assert!(!min.is_subnormal());
assert!(!max.is_subnormal());

assert!(!zero.is_subnormal());
assert!(!f128::NAN.is_subnormal());
assert!(!f128::INFINITY.is_subnormal());
// Values between `0` and `min` are Subnormal.
assert!(lower_than_min.is_subnormal());

pub const fn is_normal(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

Returns true if the number is neither zero, infinite, subnormal, or NaN.

#![feature(f128)]

let min = f128::MIN_POSITIVE; // 3.362103143e-4932f128
let max = f128::MAX;
let lower_than_min = 1.0e-4960_f128;
let zero = 0.0_f128;

assert!(min.is_normal());
assert!(max.is_normal());

assert!(!zero.is_normal());
assert!(!f128::NAN.is_normal());
assert!(!f128::INFINITY.is_normal());
// Values between `0` and `min` are Subnormal.
assert!(!lower_than_min.is_normal());

pub const fn classify(self) -> FpCategory

🔬This is a nightly-only experimental API. (f128 #116909)

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.

#![feature(f128)]

use std::num::FpCategory;

let num = 12.4_f128;
let inf = f128::INFINITY;

assert_eq!(num.classify(), FpCategory::Normal);
assert_eq!(inf.classify(), FpCategory::Infinite);

pub const fn is_sign_positive(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

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 for more info. Use self.signum() == 1.0 if you need fully portable behavior (will return false for all NaNs).

#![feature(f128)]

let f = 7.0_f128;
let g = -7.0_f128;

assert!(f.is_sign_positive());
assert!(!g.is_sign_positive());

pub const fn is_sign_negative(self) -> bool

🔬This is a nightly-only experimental API. (f128 #116909)

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 for more info. Use self.signum() == -1.0 if you need fully portable behavior (will return false for all NaNs).

#![feature(f128)]

let f = 7.0_f128;
let g = -7.0_f128;

assert!(!f.is_sign_negative());
assert!(g.is_sign_negative());

pub const fn next_up(self) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the least number greater than self.

Let TINY be the smallest representable positive f128. 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.

#![feature(f128)]
#![feature(float_next_up_down)]

// f128::EPSILON is the difference between 1.0 and the next number up.
assert_eq!(1.0f128.next_up(), 1.0 + f128::EPSILON);
// But not for most numbers.
assert!(0.1f128.next_up() < 0.1 + f128::EPSILON);
assert_eq!(4611686018427387904f128.next_up(), 4611686018427387904.000000000000001);

pub const fn next_down(self) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the greatest number less than self.

Let TINY be the smallest representable positive f128. 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.

#![feature(f128)]
#![feature(float_next_up_down)]

let x = 1.0f128;
// Clamp value into range [0, 1).
let clamped = x.clamp(0.0, 1.0f128.next_down());
assert!(clamped < 1.0);
assert_eq!(clamped.next_up(), 1.0);

pub const fn recip(self) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Takes the reciprocal (inverse) of a number, 1/x.

#![feature(f128)]

let x = 2.0_f128;
let abs_difference = (x.recip() - (1.0 / x)).abs();

assert!(abs_difference <= f128::EPSILON);

pub const fn to_degrees(self) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Converts radians to degrees.

#![feature(f128)]

let angle = std::f128::consts::PI;

let abs_difference = (angle.to_degrees() - 180.0).abs();
assert!(abs_difference <= f128::EPSILON);

pub const fn to_radians(self) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

Converts degrees to radians.

#![feature(f128)]

let angle = 180.0f128;

let abs_difference = (angle.to_radians() - std::f128::consts::PI).abs();

assert!(abs_difference <= 1e-30);

pub const fn max(self, other: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

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.

#![feature(f128)]

let x = 1.0f128;
let y = 2.0f128;

assert_eq!(x.max(y), y);

pub const fn min(self, other: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

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.

#![feature(f128)]

let x = 1.0f128;
let y = 2.0f128;

assert_eq!(x.min(y), x);

pub const fn maximum(self, other: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the maximum of the two numbers, propagating NaN.

This returns NaN when either argument is NaN, as opposed to f128::max which only returns NaN when both arguments are NaN.

#![feature(f128)]
#![feature(float_minimum_maximum)]

let x = 1.0f128;
let y = 2.0f128;

assert_eq!(x.maximum(y), y);
assert!(x.maximum(f128::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 for more info.

pub const fn minimum(self, other: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the minimum of the two numbers, propagating NaN.

This returns NaN when either argument is NaN, as opposed to f128::min which only returns NaN when both arguments are NaN.

#![feature(f128)]
#![feature(float_minimum_maximum)]

let x = 1.0f128;
let y = 2.0f128;

assert_eq!(x.minimum(y), x);
assert!(x.minimum(f128::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 for more info.

pub const fn midpoint(self, other: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

Calculates the middle point of self and rhs.

This returns NaN when either argument is NaN or if a combination of +inf and -inf is provided as arguments.

Examples

#![feature(f128)]

assert_eq!(1f128.midpoint(4.0), 2.5);
assert_eq!((-5.5f128).midpoint(8.0), 1.25);

pub unsafe fn to_int_unchecked<Int>(self) -> Int

where Self: FloatToInt<Int>,

🔬This is a nightly-only experimental API. (f128 #116909)

Rounds toward zero and converts to any primitive integer type, assuming that the value is finite and fits in that type.

#![feature(f128)]

let value = 4.6_f128;
let rounded = unsafe { value.to_int_unchecked::<u16>() };
assert_eq!(rounded, 4);

let value = -128.9_f128;
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

pub const fn to_bits(self) -> u128

🔬This is a nightly-only experimental API. (f128 #116909)

Raw transmutation to u128.

This is currently identical to transmute::<f128, u128>(self) on all platforms.

See 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.

#![feature(f128)]

assert_eq!((12.5f128).to_bits(), 0x40029000000000000000000000000000);

pub const fn from_bits(v: u128) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Raw transmutation from u128.

This is currently identical to transmute::<u128, f128>(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.

#![feature(f128)]

let v = f128::from_bits(0x40029000000000000000000000000000);
assert_eq!(v, 12.5);

pub const fn to_be_bytes(self) -> [u8; 16]

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the memory representation of this floating point number as a byte array in big-endian (network) byte order.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let bytes = 12.5f128.to_be_bytes();
assert_eq!(
    bytes,
    [0x40, 0x02, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
);

pub const fn to_le_bytes(self) -> [u8; 16]

🔬This is a nightly-only experimental API. (f128 #116909)

Returns the memory representation of this floating point number as a byte array in little-endian byte order.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let bytes = 12.5f128.to_le_bytes();
assert_eq!(
    bytes,
    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0x02, 0x40]
);

pub const fn to_ne_bytes(self) -> [u8; 16]

🔬This is a nightly-only experimental API. (f128 #116909)

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.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let bytes = 12.5f128.to_ne_bytes();
assert_eq!(
    bytes,
    if cfg!(target_endian = "big") {
        [0x40, 0x02, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
    } else {
        [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0x02, 0x40]
    }
);

pub const fn from_be_bytes(bytes: [u8; 16]) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Creates a floating point value from its representation as a byte array in big endian.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let value = f128::from_be_bytes(
    [0x40, 0x02, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
);
assert_eq!(value, 12.5);

pub const fn from_le_bytes(bytes: [u8; 16]) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Creates a floating point value from its representation as a byte array in little endian.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let value = f128::from_le_bytes(
    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0x02, 0x40]
);
assert_eq!(value, 12.5);

pub const fn from_ne_bytes(bytes: [u8; 16]) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

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.

See from_bits for some discussion of the portability of this operation (there are almost no issues).

Examples

#![feature(f128)]

let value = f128::from_ne_bytes(if cfg!(target_endian = "big") {
    [0x40, 0x02, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
} else {
    [0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     0x00, 0x00, 0x00, 0x00, 0x00, 0x90, 0x02, 0x40]
});
assert_eq!(value, 12.5);

pub fn total_cmp(&self, other: &Self) -> Ordering

🔬This is a nightly-only experimental API. (f128 #116909)

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 f128. 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

#![feature(f128)]

struct GoodBoy {
    name: &'static str,
    weight: f128,
}

let mut bois = vec![
    GoodBoy { name: "Pucci", weight: 0.1 },
    GoodBoy { name: "Woofer", weight: 99.0 },
    GoodBoy { name: "Yapper", weight: 10.0 },
    GoodBoy { name: "Chonk", weight: f128::INFINITY },
    GoodBoy { name: "Abs. Unit", weight: f128::NAN },
    GoodBoy { name: "Floaty", weight: -5.0 },
];

bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));

// `f128::NAN` could be positive or negative, which will affect the sort order.
if f128::NAN.is_sign_negative() {
    bois.into_iter().map(|b| b.weight)
        .zip([f128::NAN, -5.0, 0.1, 10.0, 99.0, f128::INFINITY].iter())
        .for_each(|(a, b)| assert_eq!(a.to_bits(), b.to_bits()))
} else {
    bois.into_iter().map(|b| b.weight)
        .zip([-5.0, 0.1, 10.0, 99.0, f128::INFINITY, f128::NAN].iter())
        .for_each(|(a, b)| assert_eq!(a.to_bits(), b.to_bits()))
}

pub const fn clamp(self, min: f128, max: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

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

#![feature(f128)]

assert!((-3.0f128).clamp(-2.0, 1.0) == -2.0);
assert!((0.0f128).clamp(-2.0, 1.0) == 0.0);
assert!((2.0f128).clamp(-2.0, 1.0) == 1.0);
assert!((f128::NAN).clamp(-2.0, 1.0).is_nan());

pub const fn abs(self) -> Self

🔬This is a nightly-only experimental API. (f128 #116909)

Computes the absolute value of self.

This function always returns the precise result.

Examples

#![feature(f128)]

let x = 3.5_f128;
let y = -3.5_f128;

assert_eq!(x.abs(), x);
assert_eq!(y.abs(), -y);

assert!(f128::NAN.abs().is_nan());

pub const fn signum(self) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

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

#![feature(f128)]

let f = 3.5_f128;

assert_eq!(f.signum(), 1.0);
assert_eq!(f128::NEG_INFINITY.signum(), -1.0);

assert!(f128::NAN.signum().is_nan());

pub const fn copysign(self, sign: f128) -> f128

🔬This is a nightly-only experimental API. (f128 #116909)

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 for more info.

Examples

#![feature(f128)]

let f = 3.5_f128;

assert_eq!(f.copysign(0.42), 3.5_f128);
assert_eq!(f.copysign(-0.42), -3.5_f128);
assert_eq!((-f).copysign(0.42), 3.5_f128);
assert_eq!((-f).copysign(-0.42), -3.5_f128);

assert!(f128::NAN.copysign(1.0).is_nan());

Trait Implementations

impl Add<&f128> for &f128

type Output = <f128 as Add>::Output

The resulting type after applying the + operator.

fn add(self, other: &f128) -> <f128 as Add<f128>>::Output

Performs the + operation.

impl Add<&f128> for f128

type Output = <f128 as Add>::Output

The resulting type after applying the + operator.

fn add(self, other: &f128) -> <f128 as Add<f128>>::Output

Performs the + operation.

impl<'a> Add<f128> for &'a f128

type Output = <f128 as Add>::Output

The resulting type after applying the + operator.

fn add(self, other: f128) -> <f128 as Add<f128>>::Output

Performs the + operation.

impl Add for f128

type Output = f128

The resulting type after applying the + operator.

const fn add(self, other: f128) -> f128

Performs the + operation.

impl AddAssign<&f128> for f128

fn add_assign(&mut self, other: &f128)

Performs the += operation.

impl AddAssign for f128

fn add_assign(&mut self, other: f128)

Performs the += operation.

impl Clone for f128

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for f128

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for f128

fn default() -> f128

Returns the default value of 0.0

impl Div<&f128> for &f128

type Output = <f128 as Div>::Output

The resulting type after applying the / operator.

fn div(self, other: &f128) -> <f128 as Div<f128>>::Output

Performs the / operation.

impl Div<&f128> for f128

type Output = <f128 as Div>::Output

The resulting type after applying the / operator.

fn div(self, other: &f128) -> <f128 as Div<f128>>::Output

Performs the / operation.

impl<'a> Div<f128> for &'a f128

type Output = <f128 as Div>::Output

The resulting type after applying the / operator.

fn div(self, other: f128) -> <f128 as Div<f128>>::Output

Performs the / operation.

impl Div for f128

type Output = f128

The resulting type after applying the / operator.

fn div(self, other: f128) -> f128

Performs the / operation.

impl DivAssign<&f128> for f128

fn div_assign(&mut self, other: &f128)

Performs the /= operation.

impl DivAssign for f128

fn div_assign(&mut self, other: f128)

Performs the /= operation.

impl From<f16> for f128

fn from(small: f16) -> Self

Converts f16 to f128 losslessly.

impl From<f32> for f128

fn from(small: f32) -> Self

Converts f32 to f128 losslessly.

impl From<f64> for f128

fn from(small: f64) -> Self

Converts f64 to f128 losslessly.

impl Mul<&f128> for &f128

type Output = <f128 as Mul>::Output

The resulting type after applying the * operator.

fn mul(self, other: &f128) -> <f128 as Mul<f128>>::Output

Performs the * operation.

impl Mul<&f128> for f128

type Output = <f128 as Mul>::Output

The resulting type after applying the * operator.

fn mul(self, other: &f128) -> <f128 as Mul<f128>>::Output

Performs the * operation.

impl<'a> Mul<f128> for &'a f128

type Output = <f128 as Mul>::Output

The resulting type after applying the * operator.

fn mul(self, other: f128) -> <f128 as Mul<f128>>::Output

Performs the * operation.

impl Mul for f128

type Output = f128

The resulting type after applying the * operator.

fn mul(self, other: f128) -> f128

Performs the * operation.

impl MulAssign<&f128> for f128

fn mul_assign(&mut self, other: &f128)

Performs the *= operation.

impl MulAssign for f128

fn mul_assign(&mut self, other: f128)

Performs the *= operation.

impl Neg for &f128

type Output = <f128 as Neg>::Output

The resulting type after applying the - operator.

fn neg(self) -> <f128 as Neg>::Output

Performs the unary - operation.

impl Neg for f128

type Output = f128

The resulting type after applying the - operator.

fn neg(self) -> f128

Performs the unary - operation.

impl PartialEq for f128

fn eq(&self, other: &f128) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &f128) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for f128

fn partial_cmp(&self, other: &f128) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &f128) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &f128) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn ge(&self, other: &f128) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

fn gt(&self, other: &f128) -> bool

Tests greater than (for self and other) and is used by the > operator.

impl Rem<&f128> for &f128

type Output = <f128 as Rem>::Output

The resulting type after applying the % operator.

fn rem(self, other: &f128) -> <f128 as Rem<f128>>::Output

Performs the % operation.

impl Rem<&f128> for f128

type Output = <f128 as Rem>::Output

The resulting type after applying the % operator.

fn rem(self, other: &f128) -> <f128 as Rem<f128>>::Output

Performs the % operation.

impl<'a> Rem<f128> for &'a f128

type Output = <f128 as Rem>::Output

The resulting type after applying the % operator.

fn rem(self, other: f128) -> <f128 as Rem<f128>>::Output

Performs the % operation.

impl Rem for f128

The remainder from the division of two floats.

The remainder has the same sign as the dividend and is computed as: x - (x / y).trunc() * y.

Examples

let x: f32 = 50.50;
let y: f32 = 8.125;
let remainder = x - (x / y).trunc() * y;

// The answer to both operations is 1.75
assert_eq!(x % y, remainder);

type Output = f128

The resulting type after applying the % operator.

fn rem(self, other: f128) -> f128

Performs the % operation.

impl RemAssign<&f128> for f128

fn rem_assign(&mut self, other: &f128)

Performs the %= operation.

impl RemAssign for f128

fn rem_assign(&mut self, other: f128)

Performs the %= operation.

impl Sub<&f128> for &f128

type Output = <f128 as Sub>::Output

The resulting type after applying the - operator.

fn sub(self, other: &f128) -> <f128 as Sub<f128>>::Output

Performs the - operation.

impl Sub<&f128> for f128

type Output = <f128 as Sub>::Output

The resulting type after applying the - operator.

fn sub(self, other: &f128) -> <f128 as Sub<f128>>::Output

Performs the - operation.

impl<'a> Sub<f128> for &'a f128

type Output = <f128 as Sub>::Output

The resulting type after applying the - operator.

fn sub(self, other: f128) -> <f128 as Sub<f128>>::Output

Performs the - operation.

impl Sub for f128

type Output = f128

The resulting type after applying the - operator.

fn sub(self, other: f128) -> f128

Performs the - operation.

impl SubAssign<&f128> for f128

fn sub_assign(&mut self, other: &f128)

Performs the -= operation.

impl SubAssign for f128

fn sub_assign(&mut self, other: f128)

Performs the -= operation.

impl Copy for f128

impl FloatToInt<i128> for f128

impl FloatToInt<i16> for f128

impl FloatToInt<i32> for f128

impl FloatToInt<i64> for f128

impl FloatToInt<i8> for f128

impl FloatToInt<isize> for f128

impl FloatToInt<u128> for f128

impl FloatToInt<u16> for f128

impl FloatToInt<u32> for f128

impl FloatToInt<u64> for f128

impl FloatToInt<u8> for f128

impl FloatToInt<usize> for f128