Primitive Type f32

A 32-bit floating point type (specifically, the "binary32" type defined in IEEE 754-2008).

This type can represent a wide range of decimal numbers, like 3.5, 27, -113.75, 0.0078125, 34359738368, 0, -1. So unlike integer types (such as i32), floating point types can represent non-integer numbers, too.

However, being able to represent this wide range of numbers comes at the cost of precision: floats can only represent some of the real numbers and calculation with floats round to a nearby representable number. For example, 5.0 and 1.0 can be exactly represented as f32, but 1.0 / 5.0 results in 0.20000000298023223876953125 since 0.2 cannot be exactly represented as f32. Note however, that printing floats with println and friends will often discard insignificant digits: println!("{}", 1.0f32 / 5.0f32) will print 0.2.

Additionally, f32 can represent a couple of special values:

• -0: this is just due to how floats are encoded. It is semantically equivalent to 0 and -0.0 == 0.0 results in true.
• ∞ and −∞: these result from calculations like 1.0 / 0.0.
• NaN (not a number): this value results from calculations like (-1.0).sqrt(). NaN has some potentially unexpected behavior: it is unequal to any float, including itself! It is also neither smaller nor greater than any float, making it impossible to sort. Lastly, it is considered infectious as almost all calculations where one of the operands is NaN will also result in NaN.

For more information on floating point numbers, see Wikipedia.

See also the std::f32::consts module.

Implementations

impl f32

#[must_use = "method returns a new number and does not mutate the original value"]pub fn floor(self) -> f32

Returns the largest integer less than or equal to a number.

Examples

let f = 3.7_f32;
let g = 3.0_f32;
let h = -3.7_f32;

assert_eq!(f.floor(), 3.0);
assert_eq!(g.floor(), 3.0);
assert_eq!(h.floor(), -4.0);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn ceil(self) -> f32

Returns the smallest integer greater than or equal to a number.

Examples

let f = 3.01_f32;
let g = 4.0_f32;

assert_eq!(f.ceil(), 4.0);
assert_eq!(g.ceil(), 4.0);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn round(self) -> f32

Returns the nearest integer to a number. Round half-way cases away from 0.0.

Examples

let f = 3.3_f32;
let g = -3.3_f32;

assert_eq!(f.round(), 3.0);
assert_eq!(g.round(), -3.0);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn trunc(self) -> f32

Returns the integer part of a number.

Examples

let f = 3.7_f32;
let g = 3.0_f32;
let h = -3.7_f32;

assert_eq!(f.trunc(), 3.0);
assert_eq!(g.trunc(), 3.0);
assert_eq!(h.trunc(), -3.0);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn fract(self) -> f32

Returns the fractional part of a number.

Examples

let x = 3.6_f32;
let y = -3.6_f32;
let abs_difference_x = (x.fract() - 0.6).abs();
let abs_difference_y = (y.fract() - (-0.6)).abs();

assert!(abs_difference_x <= f32::EPSILON);
assert!(abs_difference_y <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn abs(self) -> f32

Computes the absolute value of self. Returns NAN if the number is NAN.

Examples

let x = 3.5_f32;
let y = -3.5_f32;

let abs_difference_x = (x.abs() - x).abs();
let abs_difference_y = (y.abs() - (-y)).abs();

assert!(abs_difference_x <= f32::EPSILON);
assert!(abs_difference_y <= f32::EPSILON);

assert!(f32::NAN.abs().is_nan());

#[must_use = "method returns a new number and does not mutate the original value"]pub fn signum(self) -> f32

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"]pub fn copysign(self, sign: f32) -> f32

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 sign of sign is returned.

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"]pub fn mul_add(self, a: f32, b: f32) -> f32

Fused multiply-add. Computes (self * a) + b with only one rounding error, yielding a more accurate result than an unfused multiply-add.

Using mul_add can be more performant than an unfused multiply-add if the target architecture has a dedicated fma CPU instruction.

Examples

let m = 10.0_f32;
let x = 4.0_f32;
let b = 60.0_f32;

// 100.0
let abs_difference = (m.mul_add(x, b) - ((m * x) + b)).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn div_euclid(self, rhs: f32) -> f32

Calculates Euclidean division, the matching method for rem_euclid.

This computes the integer n such that self = n * rhs + self.rem_euclid(rhs). In other words, the result is self / rhs rounded to the integer n such that self >= n * rhs.

Examples

let a: f32 = 7.0;
let b = 4.0;
assert_eq!(a.div_euclid(b), 1.0); // 7.0 > 4.0 * 1.0
assert_eq!((-a).div_euclid(b), -2.0); // -7.0 >= 4.0 * -2.0
assert_eq!(a.div_euclid(-b), -1.0); // 7.0 >= -4.0 * -1.0
assert_eq!((-a).div_euclid(-b), 2.0); // -7.0 >= -4.0 * 2.0

#[must_use = "method returns a new number and does not mutate the original value"]pub fn rem_euclid(self, rhs: f32) -> f32

Calculates the least nonnegative remainder of self (mod rhs).

In particular, the return value r satisfies 0.0 <= r < rhs.abs() in most cases. However, due to a floating point round-off error it can result in r == rhs.abs(), violating the mathematical definition, if self is much smaller than rhs.abs() in magnitude and self < 0.0. This result is not an element of the function's codomain, but it is the closest floating point number in the real numbers and thus fulfills the property self == self.div_euclid(rhs) * rhs + self.rem_euclid(rhs) approximatively.

Examples

let a: f32 = 7.0;
let b = 4.0;
assert_eq!(a.rem_euclid(b), 3.0);
assert_eq!((-a).rem_euclid(b), 1.0);
assert_eq!(a.rem_euclid(-b), 3.0);
assert_eq!((-a).rem_euclid(-b), 1.0);
// limitation due to round-off error
assert!((-f32::EPSILON).rem_euclid(3.0) != 0.0);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn powi(self, n: i32) -> f32

Raises a number to an integer power.

Using this function is generally faster than using powf

Examples

let x = 2.0_f32;
let abs_difference = (x.powi(2) - (x * x)).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn powf(self, n: f32) -> f32

Raises a number to a floating point power.

Examples

let x = 2.0_f32;
let abs_difference = (x.powf(2.0) - (x * x)).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn sqrt(self) -> f32

Returns the square root of a number.

Returns NaN if self is a negative number.

Examples

let positive = 4.0_f32;
let negative = -4.0_f32;

let abs_difference = (positive.sqrt() - 2.0).abs();

assert!(abs_difference <= f32::EPSILON);
assert!(negative.sqrt().is_nan());

#[must_use = "method returns a new number and does not mutate the original value"]pub fn exp(self) -> f32

Returns e^(self), (the exponential function).

Examples

let one = 1.0f32;
// e^1
let e = one.exp();

// ln(e) - 1 == 0
let abs_difference = (e.ln() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn exp2(self) -> f32

Returns 2^(self).

Examples

let f = 2.0f32;

// 2^2 - 4 == 0
let abs_difference = (f.exp2() - 4.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn ln(self) -> f32

Returns the natural logarithm of the number.

Examples

let one = 1.0f32;
// e^1
let e = one.exp();

// ln(e) - 1 == 0
let abs_difference = (e.ln() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn log(self, base: f32) -> f32

Returns the logarithm of the number with respect to an arbitrary base.

The result may not be correctly rounded owing to implementation details; self.log2() can produce more accurate results for base 2, and self.log10() can produce more accurate results for base 10.

Examples

let five = 5.0f32;

// log5(5) - 1 == 0
let abs_difference = (five.log(5.0) - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn log2(self) -> f32

Returns the base 2 logarithm of the number.

Examples

let two = 2.0f32;

// log2(2) - 1 == 0
let abs_difference = (two.log2() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn log10(self) -> f32

Returns the base 10 logarithm of the number.

Examples

let ten = 10.0f32;

// log10(10) - 1 == 0
let abs_difference = (ten.log10() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn abs_sub(self, other: f32) -> f32

👎 Deprecated since 1.10.0:

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).

The positive difference of two numbers.

• If self <= other: 0:0
• Else: self - other

Examples

let x = 3.0f32;
let y = -3.0f32;

let abs_difference_x = (x.abs_sub(1.0) - 2.0).abs();
let abs_difference_y = (y.abs_sub(1.0) - 0.0).abs();

assert!(abs_difference_x <= f32::EPSILON);
assert!(abs_difference_y <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn cbrt(self) -> f32

Returns the cubic root of a number.

Examples

let x = 8.0f32;

// x^(1/3) - 2 == 0
let abs_difference = (x.cbrt() - 2.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn hypot(self, other: f32) -> f32

Calculates the length of the hypotenuse of a right-angle triangle given legs of length x and y.

Examples

let x = 2.0f32;
let y = 3.0f32;

// sqrt(x^2 + y^2)
let abs_difference = (x.hypot(y) - (x.powi(2) + y.powi(2)).sqrt()).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn sin(self) -> f32

Computes the sine of a number (in radians).

Examples

let x = std::f32::consts::FRAC_PI_2;

let abs_difference = (x.sin() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn cos(self) -> f32

Computes the cosine of a number (in radians).

Examples

let x = 2.0 * std::f32::consts::PI;

let abs_difference = (x.cos() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn tan(self) -> f32

Computes the tangent of a number (in radians).

Examples

let x = std::f32::consts::FRAC_PI_4;
let abs_difference = (x.tan() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn asin(self) -> f32

Computes the arcsine of a number. Return value is in radians in the range [-pi/2, pi/2] or NaN if the number is outside the range [-1, 1].

Examples

let f = std::f32::consts::FRAC_PI_2;

// asin(sin(pi/2))
let abs_difference = (f.sin().asin() - std::f32::consts::FRAC_PI_2).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn acos(self) -> f32

Computes the arccosine of a number. Return value is in radians in the range [0, pi] or NaN if the number is outside the range [-1, 1].

Examples

let f = std::f32::consts::FRAC_PI_4;

// acos(cos(pi/4))
let abs_difference = (f.cos().acos() - std::f32::consts::FRAC_PI_4).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn atan(self) -> f32

Computes the arctangent of a number. Return value is in radians in the range [-pi/2, pi/2];

Examples

let f = 1.0f32;

// atan(tan(1))
let abs_difference = (f.tan().atan() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn atan2(self, other: f32) -> f32

Computes the four quadrant arctangent of self (y) and other (x) in radians.

• x = 0, y = 0: 0
• x >= 0: arctan(y/x) -> [-pi/2, pi/2]
• y >= 0: arctan(y/x) + pi -> (pi/2, pi]
• y < 0: arctan(y/x) - pi -> (-pi, -pi/2)

Examples

// Positive angles measured counter-clockwise
// from positive x axis
// -pi/4 radians (45 deg clockwise)
let x1 = 3.0f32;
let y1 = -3.0f32;

// 3pi/4 radians (135 deg counter-clockwise)
let x2 = -3.0f32;
let y2 = 3.0f32;

let abs_difference_1 = (y1.atan2(x1) - (-std::f32::consts::FRAC_PI_4)).abs();
let abs_difference_2 = (y2.atan2(x2) - (3.0 * std::f32::consts::FRAC_PI_4)).abs();

assert!(abs_difference_1 <= f32::EPSILON);
assert!(abs_difference_2 <= f32::EPSILON);

pub fn sin_cos(self) -> (f32, f32)

Simultaneously computes the sine and cosine of the number, x. Returns (sin(x), cos(x)).

Examples

let x = std::f32::consts::FRAC_PI_4;
let f = x.sin_cos();

let abs_difference_0 = (f.0 - x.sin()).abs();
let abs_difference_1 = (f.1 - x.cos()).abs();

assert!(abs_difference_0 <= f32::EPSILON);
assert!(abs_difference_1 <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn exp_m1(self) -> f32

Returns e^(self) - 1 in a way that is accurate even if the number is close to zero.

Examples

let x = 6.0f32;

// e^(ln(6)) - 1
let abs_difference = (x.ln().exp_m1() - 5.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn ln_1p(self) -> f32

Returns ln(1+n) (natural logarithm) more accurately than if the operations were performed separately.

Examples

let x = std::f32::consts::E - 1.0;

// ln(1 + (e - 1)) == ln(e) == 1
let abs_difference = (x.ln_1p() - 1.0).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn sinh(self) -> f32

Hyperbolic sine function.

Examples

let e = std::f32::consts::E;
let x = 1.0f32;

let f = x.sinh();
// Solving sinh() at 1 gives `(e^2-1)/(2e)`
let g = ((e * e) - 1.0) / (2.0 * e);
let abs_difference = (f - g).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn cosh(self) -> f32

Hyperbolic cosine function.

Examples

let e = std::f32::consts::E;
let x = 1.0f32;
let f = x.cosh();
// Solving cosh() at 1 gives this result
let g = ((e * e) + 1.0) / (2.0 * e);
let abs_difference = (f - g).abs();

// Same result
assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn tanh(self) -> f32

Hyperbolic tangent function.

Examples

let e = std::f32::consts::E;
let x = 1.0f32;

let f = x.tanh();
// Solving tanh() at 1 gives `(1 - e^(-2))/(1 + e^(-2))`
let g = (1.0 - e.powi(-2)) / (1.0 + e.powi(-2));
let abs_difference = (f - g).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn asinh(self) -> f32

Inverse hyperbolic sine function.

Examples

let x = 1.0f32;
let f = x.sinh().asinh();

let abs_difference = (f - x).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn acosh(self) -> f32

Inverse hyperbolic cosine function.

Examples

let x = 1.0f32;
let f = x.cosh().acosh();

let abs_difference = (f - x).abs();

assert!(abs_difference <= f32::EPSILON);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn atanh(self) -> f32

Inverse hyperbolic tangent function.

Examples

let e = std::f32::consts::E;
let f = e.tanh().atanh();

let abs_difference = (f - e).abs();

assert!(abs_difference <= 1e-5);

#[must_use = "method returns a new number and does not mutate the original value"]pub fn clamp(self, min: f32, max: f32) -> f32

🔬 This is a nightly-only experimental API. (clamp #44095)

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(clamp)]
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());

impl f32

pub const RADIX: u32

The radix or base of the internal representation of f32.

pub const MANTISSA_DIGITS: u32

Number of significant digits in base 2.

pub const DIGITS: u32

Approximate number of significant digits in base 10.

pub const EPSILON: f32

Machine epsilon value for f32.

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

pub const MIN: f32

Smallest finite f32 value.

pub const MIN_POSITIVE: f32

Smallest positive normal f32 value.

pub const MAX: f32

Largest finite f32 value.

pub const MIN_EXP: i32

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

pub const MAX_EXP: i32

Maximum possible power of 2 exponent.

pub const MIN_10_EXP: i32

Minimum possible normal power of 10 exponent.

pub const MAX_10_EXP: i32

Maximum possible power of 10 exponent.

pub const NAN: f32

Not a Number (NaN).

pub const INFINITY: f32

Infinity (∞).

pub const NEG_INFINITY: f32

Negative infinity (−∞).

pub fn is_nan(self) -> bool

Returns true if this value is NaN.

let nan = f32::NAN;
let f = 7.0_f32;

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

pub fn is_infinite(self) -> bool

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());

pub fn is_finite(self) -> bool

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());

pub fn is_normal(self) -> bool

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());

pub fn classify(self) -> FpCategory

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);

pub fn is_sign_positive(self) -> bool

Returns true if self has a positive sign, including +0.0, NaNs with positive sign bit and positive infinity.

let f = 7.0_f32;
let g = -7.0_f32;

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

pub fn is_sign_negative(self) -> bool

Returns true if self has a negative sign, including -0.0, NaNs with negative sign bit and negative infinity.

let f = 7.0f32;
let g = -7.0f32;

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

pub fn recip(self) -> f32

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);

pub fn to_degrees(self) -> f32

Converts radians to degrees.

let angle = std::f32::consts::PI;

let abs_difference = (angle.to_degrees() - 180.0).abs();

assert!(abs_difference <= f32::EPSILON);

pub fn to_radians(self) -> f32

Converts degrees to radians.

let angle = 180.0f32;

let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();

assert!(abs_difference <= f32::EPSILON);

pub fn max(self, other: f32) -> f32

Returns the maximum of the two numbers.

let x = 1.0f32;
let y = 2.0f32;

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

If one of the arguments is NaN, then the other argument is returned.

pub fn min(self, other: f32) -> f32

Returns the minimum of the two numbers.

let x = 1.0f32;
let y = 2.0f32;

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

If one of the arguments is NaN, then the other argument is returned.

pub unsafe fn to_int_unchecked<Int>(self) -> Int where
    f32: FloatToInt<Int>, 

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::<u16>() };
assert_eq!(rounded, 4);

let value = -128.9_f32;
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 fn to_bits(self) -> u32

Raw transmutation to u32.

This is currently identical to transmute::<f32, u32>(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.

Examples

assert_ne!((1f32).to_bits(), 1f32 as u32); // to_bits() is not casting!
assert_eq!((12.5f32).to_bits(), 0x41480000);

pub fn from_bits(v: u32) -> f32

Raw transmutation from u32.

This is currently identical to transmute::<u32, f32>(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);

pub fn to_be_bytes(self) -> [u8; 4]

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

Examples

let bytes = 12.5f32.to_be_bytes();
assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);

pub fn to_le_bytes(self) -> [u8; 4]

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

Examples

let bytes = 12.5f32.to_le_bytes();
assert_eq!(bytes, [0x00, 0x00, 0x48, 0x41]);

pub fn to_ne_bytes(self) -> [u8; 4]

Return the memory representation of this floating point number as a byte array in native byte order.

As the target platform's native endianness is used, portable code should use to_be_bytes or to_le_bytes, as appropriate, instead.

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]
    }
);

pub fn from_be_bytes(bytes: [u8; 4]) -> f32

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

Examples

let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
assert_eq!(value, 12.5);

pub fn from_le_bytes(bytes: [u8; 4]) -> f32

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

Examples

let value = f32::from_le_bytes([0x00, 0x00, 0x48, 0x41]);
assert_eq!(value, 12.5);

pub fn from_ne_bytes(bytes: [u8; 4]) -> f32

Create a floating point value from its representation as a byte array in native endian.

As the target platform's native endianness is used, portable code likely wants to use from_be_bytes or from_le_bytes, as appropriate instead.

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);

pub fn total_cmp(&self, other: &f32) -> Ordering

🔬 This is a nightly-only experimental API. (total_cmp #72599)

Returns an ordering between self and other values. Unlike the standard partial comparison between floating point numbers, this comparison always produces an ordering in accordance to the totalOrder predicate as defined in IEEE 754 (2008 revision) floating point standard. The values are ordered in following order:

• 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

Example

#![feature(total_cmp)]
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));

Trait Implementations

impl<'_> Add<&'_ f32> for f32

type Output = <f32 as Add<f32>>::Output

The resulting type after applying the + operator.

fn add(self, other: &f32) -> <f32 as Add<f32>>::Output

Performs the + operation.

impl<'_, '_> Add<&'_ f32> for &'_ f32

type Output = <f32 as Add<f32>>::Output

The resulting type after applying the + operator.

fn add(self, other: &f32) -> <f32 as Add<f32>>::Output

Performs the + operation.

impl Add<f32> for f32

type Output = f32

The resulting type after applying the + operator.

fn add(self, other: f32) -> f32

Performs the + operation.

impl<'a> Add<f32> for &'a f32

type Output = <f32 as Add<f32>>::Output

The resulting type after applying the + operator.

fn add(self, other: f32) -> <f32 as Add<f32>>::Output

Performs the + operation.

impl<'_> AddAssign<&'_ f32> for f32

fn add_assign(&mut self, other: &f32)

Performs the += operation.

impl AddAssign<f32> for f32

fn add_assign(&mut self, other: f32)

Performs the += operation.

impl Clone for f32

fn clone(&self) -> f32

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Copy for f32

impl Debug for f32

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

Formats the value using the given formatter.

impl Default for f32

fn default() -> f32

Returns the default value of 0.0

impl Display for f32

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

Formats the value using the given formatter.

impl<'_> Div<&'_ f32> for f32

type Output = <f32 as Div<f32>>::Output

The resulting type after applying the / operator.

fn div(self, other: &f32) -> <f32 as Div<f32>>::Output

Performs the / operation.

impl<'_, '_> Div<&'_ f32> for &'_ f32

type Output = <f32 as Div<f32>>::Output

The resulting type after applying the / operator.

fn div(self, other: &f32) -> <f32 as Div<f32>>::Output

Performs the / operation.

impl<'a> Div<f32> for &'a f32

type Output = <f32 as Div<f32>>::Output

The resulting type after applying the / operator.

fn div(self, other: f32) -> <f32 as Div<f32>>::Output

Performs the / operation.

impl Div<f32> for f32

type Output = f32

The resulting type after applying the / operator.

fn div(self, other: f32) -> f32

Performs the / operation.

impl<'_> DivAssign<&'_ f32> for f32

fn div_assign(&mut self, other: &f32)

Performs the /= operation.

impl DivAssign<f32> for f32

fn div_assign(&mut self, other: f32)

Performs the /= operation.

impl FloatToInt<i128> for f32

impl FloatToInt<i16> for f32

impl FloatToInt<i32> for f32

impl FloatToInt<i64> for f32

impl FloatToInt<i8> for f32

impl FloatToInt<isize> for f32

impl FloatToInt<u128> for f32

impl FloatToInt<u16> for f32

impl FloatToInt<u32> for f32

impl FloatToInt<u64> for f32

impl FloatToInt<u8> for f32

impl FloatToInt<usize> for f32

impl From<i16> for f32

Converts i16 to f32 losslessly.

fn from(small: i16) -> f32

Performs the conversion.

impl From<i8> for f32

Converts i8 to f32 losslessly.

fn from(small: i8) -> f32

Performs the conversion.

impl From<u16> for f32

Converts u16 to f32 losslessly.

fn from(small: u16) -> f32

Performs the conversion.

impl From<u8> for f32

Converts u8 to f32 losslessly.

fn from(small: u8) -> f32

Performs the conversion.

impl FromStr for f32

type Err = ParseFloatError

The associated error which can be returned from parsing.

fn from_str(src: &str) -> Result<f32, ParseFloatError>

Converts a string in base 10 to a float. Accepts an optional decimal exponent.

This function accepts strings such as

• '3.14'
• '-3.14'
• '2.5E10', or equivalently, '2.5e10'
• '2.5E-10'
• '5.'
• '.5', or, equivalently, '0.5'
• 'inf', '-inf', 'NaN'

Leading and trailing whitespace represent an error.

Grammar

All strings that adhere to the following EBNF grammar will result in an Ok being returned:

Float  ::= Sign? ( 'inf' | 'NaN' | Number )
Number ::= ( Digit+ |
             Digit+ '.' Digit* |
             Digit* '.' Digit+ ) Exp?
Exp    ::= [eE] Sign? Digit+
Sign   ::= [+-]
Digit  ::= [0-9]

Known bugs

In some situations, some strings that should create a valid float instead return an error. See issue #31407 for details.

Arguments

• src - A string

Return value

Err(ParseFloatError) if the string did not represent a valid number. Otherwise, Ok(n) where n is the floating-point number represented by src.

impl LowerExp for f32

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

Formats the value using the given formatter.

impl<'_, '_> Mul<&'_ f32> for &'_ f32

type Output = <f32 as Mul<f32>>::Output

The resulting type after applying the * operator.

fn mul(self, other: &f32) -> <f32 as Mul<f32>>::Output

Performs the * operation.

impl<'_> Mul<&'_ f32> for f32

type Output = <f32 as Mul<f32>>::Output

The resulting type after applying the * operator.

fn mul(self, other: &f32) -> <f32 as Mul<f32>>::Output

Performs the * operation.

impl Mul<f32> for f32

type Output = f32

The resulting type after applying the * operator.

fn mul(self, other: f32) -> f32

Performs the * operation.

impl<'a> Mul<f32> for &'a f32

type Output = <f32 as Mul<f32>>::Output

The resulting type after applying the * operator.

fn mul(self, other: f32) -> <f32 as Mul<f32>>::Output

Performs the * operation.

impl<'_> MulAssign<&'_ f32> for f32

fn mul_assign(&mut self, other: &f32)

Performs the *= operation.

impl MulAssign<f32> for f32

fn mul_assign(&mut self, other: f32)

Performs the *= operation.

impl Neg for f32

type Output = f32

The resulting type after applying the - operator.

fn neg(self) -> f32

Performs the unary - operation.

impl<'_> Neg for &'_ f32

type Output = <f32 as Neg>::Output

The resulting type after applying the - operator.

fn neg(self) -> <f32 as Neg>::Output

Performs the unary - operation.

impl PartialEq<f32> for f32

fn eq(&self, other: &f32) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &f32) -> bool

This method tests for !=.

impl PartialOrd<f32> for f32

fn partial_cmp(&self, other: &f32) -> Option<Ordering>

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

fn lt(&self, other: &f32) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &f32) -> bool

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

fn ge(&self, other: &f32) -> bool

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

fn gt(&self, other: &f32) -> bool

This method tests greater than (for self and other) and is used by the > operator.

impl<'a> Product<&'a f32> for f32

fn product<I>(iter: I) -> f32 where
    I: Iterator<Item = &'a f32>, 

Method which takes an iterator and generates Self from the elements by multiplying the items.

impl Product<f32> for f32

fn product<I>(iter: I) -> f32 where
    I: Iterator<Item = f32>, 

Method which takes an iterator and generates Self from the elements by multiplying the items.

impl<'_, '_> Rem<&'_ f32> for &'_ f32

type Output = <f32 as Rem<f32>>::Output

The resulting type after applying the % operator.

fn rem(self, other: &f32) -> <f32 as Rem<f32>>::Output

Performs the % operation.

impl<'_> Rem<&'_ f32> for f32

type Output = <f32 as Rem<f32>>::Output

The resulting type after applying the % operator.

fn rem(self, other: &f32) -> <f32 as Rem<f32>>::Output

Performs the % operation.

impl<'a> Rem<f32> for &'a f32

type Output = <f32 as Rem<f32>>::Output

The resulting type after applying the % operator.

fn rem(self, other: f32) -> <f32 as Rem<f32>>::Output

Performs the % operation.

impl Rem<f32> for f32

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 = f32

The resulting type after applying the % operator.

fn rem(self, other: f32) -> f32

Performs the % operation.

impl<'_> RemAssign<&'_ f32> for f32

fn rem_assign(&mut self, other: &f32)

Performs the %= operation.

impl RemAssign<f32> for f32

fn rem_assign(&mut self, other: f32)

Performs the %= operation.

impl<'_, '_> Sub<&'_ f32> for &'_ f32

type Output = <f32 as Sub<f32>>::Output

The resulting type after applying the - operator.

fn sub(self, other: &f32) -> <f32 as Sub<f32>>::Output

Performs the - operation.

impl<'_> Sub<&'_ f32> for f32

type Output = <f32 as Sub<f32>>::Output

The resulting type after applying the - operator.

fn sub(self, other: &f32) -> <f32 as Sub<f32>>::Output

Performs the - operation.

impl<'a> Sub<f32> for &'a f32

type Output = <f32 as Sub<f32>>::Output

The resulting type after applying the - operator.

fn sub(self, other: f32) -> <f32 as Sub<f32>>::Output

Performs the - operation.

impl Sub<f32> for f32

type Output = f32

The resulting type after applying the - operator.

fn sub(self, other: f32) -> f32

Performs the - operation.

impl<'_> SubAssign<&'_ f32> for f32

fn sub_assign(&mut self, other: &f32)

Performs the -= operation.

impl SubAssign<f32> for f32

fn sub_assign(&mut self, other: f32)

Performs the -= operation.

impl<'a> Sum<&'a f32> for f32

fn sum<I>(iter: I) -> f32 where
    I: Iterator<Item = &'a f32>, 

Method which takes an iterator and generates Self from the elements by "summing up" the items.

impl Sum<f32> for f32

fn sum<I>(iter: I) -> f32 where
    I: Iterator<Item = f32>, 

Method which takes an iterator and generates Self from the elements by "summing up" the items.

impl UpperExp for f32

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

Formats the value using the given formatter.