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 some special values:
- −0.0: IEEE 754 floating point numbers have a bit that indicates their sign, so −0.0 is a possible value. For comparison −0.0 = +0.0, but floating point operations can carry the sign bit through arithmetic operations. This means −0.0 × +0.0 produces −0.0 and a negative number rounded to a value smaller than a float can represent also produces −0.0.
-
∞ 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
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);
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);
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);
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);
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);
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());
pub fn signum(self) -> f32
Returns a number that represents the sign of self
.
-
1.0
if the number is positive,+0.0
orINFINITY
-
-1.0
if the number is negative,-0.0
orNEG_INFINITY
-
NAN
if the number isNAN
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());
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());
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
may be more performant than an unfused multiply-add if the target architecture has a dedicated fma
CPU instruction. However, this is not always true, and will be heavily dependant on designing algorithms with specific target hardware in mind.
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);
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
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);
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);
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);
pub fn sqrt(self) -> f32
Returns the square root of a number.
Returns NaN if self
is a negative number other than -0.0
.
Examples
let positive = 4.0_f32; let negative = -4.0_f32; let negative_zero = -0.0_f32; let abs_difference = (positive.sqrt() - 2.0).abs(); assert!(abs_difference <= f32::EPSILON); assert!(negative.sqrt().is_nan()); assert!(negative_zero.sqrt() == negative_zero);
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);
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);
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);
pub fn log(self, base: f32) -> f32
Returns the logarithm of the number with respect to an arbitrary base.
The result might 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);
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);
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);
pub fn abs_sub(self, other: f32) -> f32
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);
pub fn cbrt(self) -> f32
Returns the cube 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);
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);
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);
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);
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);
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);
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);
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);
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);
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 = 1e-8_f32; // for very small x, e^x is approximately 1 + x + x^2 / 2 let approx = x + x * x / 2.0; let abs_difference = (x.exp_m1() - approx).abs(); assert!(abs_difference < 1e-10);
pub fn ln_1p(self) -> f32
Returns ln(1+n)
(natural logarithm) more accurately than if the operations were performed separately.
Examples
let x = 1e-8_f32; // for very small x, ln(1 + x) is approximately x - x^2 / 2 let approx = x - x * x / 2.0; let abs_difference = (x.ln_1p() - approx).abs(); assert!(abs_difference < 1e-10);
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);
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);
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);
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);
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);
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);
pub fn lerp(self, start: f32, end: f32) -> f32
Linear interpolation between start
and end
.
This enables linear interpolation between start
and end
, where start is represented by self == 0.0
and end
is represented by self == 1.0
. This is the basis of all “transition”, “easing”, or “step” functions; if you change self
from 0.0 to 1.0 at a given rate, the result will change from start
to end
at a similar rate.
Values below 0.0 or above 1.0 are allowed, allowing you to extrapolate values outside the range from start
to end
. This also is useful for transition functions which might move slightly past the end or start for a desired effect. Mathematically, the values returned are equivalent to start + self * (end - start)
, although we make a few specific guarantees that are useful specifically to linear interpolation.
These guarantees are:
- If
start
andend
are finite, the value at 0.0 is alwaysstart
and the value at 1.0 is alwaysend
. (exactness) - If
start
andend
are finite, the values will always move in the direction fromstart
toend
(monotonicity) - If
self
is finite andstart == end
, the value at any point will always bestart == end
. (consistency)
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 (−∞).
Returns true
if this value is NaN
.
let nan = f32::NAN; let f = 7.0_f32; assert!(nan.is_nan()); assert!(!f.is_nan());
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());
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());
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());
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());
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);
Returns true
if self
has a positive sign, including +0.0
, NaN
s 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());
Returns true
if self
has a negative sign, including -0.0
, NaN
s 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
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);
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);
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]);
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]);
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] } );
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);
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);
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
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
Note that this function does not always agree with the PartialOrd
and PartialEq
implementations of f32
. In particular, they regard negative and positive zero as equal, while total_cmp
doesn’t.
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));
pub fn clamp(self, min: f32, max: f32) -> f32
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());
Trait Implementations
impl<'_> Add<&'_ f32> for f32
type Output = <f32 as Add<f32>>::Output
The resulting type after applying the +
operator.
pub fn add(self, other: &f32) -> <f32 as Add<f32>>::Output
Performs the +
operation. Read more
impl<'_, '_> Add<&'_ f32> for &'_ f32
type Output = <f32 as Add<f32>>::Output
The resulting type after applying the +
operator.
pub fn add(self, other: &f32) -> <f32 as Add<f32>>::Output
Performs the +
operation. Read more
impl<'a> Add<f32> for &'a f32
type Output = <f32 as Add<f32>>::Output
The resulting type after applying the +
operator.
pub fn add(self, other: f32) -> <f32 as Add<f32>>::Output
Performs the +
operation. Read more
impl Add<f32> for f32
type Output = f32
The resulting type after applying the +
operator.
pub fn add(self, other: f32) -> f32
Performs the +
operation. Read more
impl<'_> AddAssign<&'_ f32> for f32
impl AddAssign<f32> for f32
impl Clone for f32
pub fn clone(&self) -> f32
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
impl Debug for f32
pub fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
pub fn default() -> f32
Returns the default value of 0.0
impl Display for f32
pub fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl<'_, '_> Div<&'_ f32> for &'_ f32
type Output = <f32 as Div<f32>>::Output
The resulting type after applying the /
operator.
pub fn div(self, other: &f32) -> <f32 as Div<f32>>::Output
Performs the /
operation. Read more
impl<'_> Div<&'_ f32> for f32
type Output = <f32 as Div<f32>>::Output
The resulting type after applying the /
operator.
pub fn div(self, other: &f32) -> <f32 as Div<f32>>::Output
Performs the /
operation. Read more
impl Div<f32> for f32
type Output = f32
The resulting type after applying the /
operator.
pub fn div(self, other: f32) -> f32
Performs the /
operation. Read more
impl<'a> Div<f32> for &'a f32
type Output = <f32 as Div<f32>>::Output
The resulting type after applying the /
operator.
pub fn div(self, other: f32) -> <f32 as Div<f32>>::Output
Performs the /
operation. Read more
impl<'_> DivAssign<&'_ f32> for f32
impl DivAssign<f32> for f32
pub fn from(small: i16) -> f32
Converts i16
to f32
losslessly.
pub fn from(small: i8) -> f32
Converts i8
to f32
losslessly.
pub fn from(small: u16) -> f32
Converts u16
to f32
losslessly.
pub fn from(small: u8) -> f32
Converts u8
to f32
losslessly.
impl FromStr for f32
pub 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]
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
.
type Err = ParseFloatError
The associated error which can be returned from parsing.
impl LowerExp for f32
pub 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.
pub fn mul(self, other: &f32) -> <f32 as Mul<f32>>::Output
Performs the *
operation. Read more
impl<'_, '_> Mul<&'_ f32> for &'_ f32
type Output = <f32 as Mul<f32>>::Output
The resulting type after applying the *
operator.
pub fn mul(self, other: &f32) -> <f32 as Mul<f32>>::Output
Performs the *
operation. Read more
impl Mul<f32> for f32
type Output = f32
The resulting type after applying the *
operator.
pub fn mul(self, other: f32) -> f32
Performs the *
operation. Read more
impl<'a> Mul<f32> for &'a f32
type Output = <f32 as Mul<f32>>::Output
The resulting type after applying the *
operator.
pub fn mul(self, other: f32) -> <f32 as Mul<f32>>::Output
Performs the *
operation. Read more
impl<'_> MulAssign<&'_ f32> for f32
impl MulAssign<f32> for f32
impl Neg for f32
type Output = f32
The resulting type after applying the -
operator.
pub fn neg(self) -> f32
Performs the unary -
operation. Read more
impl<'_> Neg for &'_ f32
type Output = <f32 as Neg>::Output
The resulting type after applying the -
operator.
pub fn neg(self) -> <f32 as Neg>::Output
Performs the unary -
operation. Read more
impl PartialEq<f32> for f32
pub fn eq(&self, other: &f32) -> bool
This method tests for self
and other
values to be equal, and is used by ==
. Read more
pub fn ne(&self, other: &f32) -> bool
This method tests for !=
.
impl PartialOrd<f32> for f32
pub fn partial_cmp(&self, other: &f32) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
pub fn lt(&self, other: &f32) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
pub fn le(&self, other: &f32) -> bool
This method tests less than or equal to (for self
and other
) and is used by the <=
operator. Read more
pub fn ge(&self, other: &f32) -> bool
This method tests greater than or equal to (for self
and other
) and is used by the >=
operator. Read more
pub fn gt(&self, other: &f32) -> bool
This method tests greater than (for self
and other
) and is used by the >
operator. Read more
impl<'a> Product<&'a f32> for f32
Method which takes an iterator and generates Self
from the elements by multiplying the items. Read more
impl Product<f32> for f32
Method which takes an iterator and generates Self
from the elements by multiplying the items. Read more
impl<'_> Rem<&'_ f32> for f32
type Output = <f32 as Rem<f32>>::Output
The resulting type after applying the %
operator.
pub fn rem(self, other: &f32) -> <f32 as Rem<f32>>::Output
Performs the %
operation. Read more
impl<'_, '_> Rem<&'_ f32> for &'_ f32
type Output = <f32 as Rem<f32>>::Output
The resulting type after applying the %
operator.
pub fn rem(self, other: &f32) -> <f32 as Rem<f32>>::Output
Performs the %
operation. Read more
impl<'a> Rem<f32> for &'a f32
type Output = <f32 as Rem<f32>>::Output
The resulting type after applying the %
operator.
pub fn rem(self, other: f32) -> <f32 as Rem<f32>>::Output
Performs the %
operation. Read more
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.
pub fn rem(self, other: f32) -> f32
Performs the %
operation. Read more
impl<'_> RemAssign<&'_ f32> for f32
impl RemAssign<f32> for f32
impl<'_> Sub<&'_ f32> for f32
type Output = <f32 as Sub<f32>>::Output
The resulting type after applying the -
operator.
pub fn sub(self, other: &f32) -> <f32 as Sub<f32>>::Output
Performs the -
operation. Read more
impl<'_, '_> Sub<&'_ f32> for &'_ f32
type Output = <f32 as Sub<f32>>::Output
The resulting type after applying the -
operator.
pub fn sub(self, other: &f32) -> <f32 as Sub<f32>>::Output
Performs the -
operation. Read more
impl Sub<f32> for f32
type Output = f32
The resulting type after applying the -
operator.
pub fn sub(self, other: f32) -> f32
Performs the -
operation. Read more
impl<'a> Sub<f32> for &'a f32
type Output = <f32 as Sub<f32>>::Output
The resulting type after applying the -
operator.
pub fn sub(self, other: f32) -> <f32 as Sub<f32>>::Output
Performs the -
operation. Read more
impl<'_> SubAssign<&'_ f32> for f32
impl SubAssign<f32> for f32
impl<'a> Sum<&'a f32> for f32
Method which takes an iterator and generates Self
from the elements by “summing up” the items. Read more
impl Sum<f32> for f32
Method which takes an iterator and generates Self
from the elements by “summing up” the items. Read more
impl UpperExp for f32
pub fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter.
impl Copy for f32
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
Auto Trait Implementations
impl RefUnwindSafe for f32
impl Send for f32
impl Sync for f32
impl Unpin for f32
impl UnwindSafe for f32
Blanket Implementations
impl<T> From<T> for T
pub fn from(t: T) -> T
Performs the conversion.
pub fn into(self) -> U
Performs the conversion.
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
pub fn clone_into(&self, target: &mut T)
toowned_clone_into
#41263)recently added
Uses borrowed data to replace owned data, usually by cloning. Read more
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/primitive.f32.html