Primitive Type f321.0.0 [−]

[−]

The 32-bit floating point type.

See also the std::f32 module.

Methods

impl f32
[src]
[−]

[−]

Returns true if this value is NaN and false otherwise.

use std::f32;

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

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

[−]

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

use std::f32;

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());Run

[−]

Returns true if this number is neither infinite nor NaN.

use std::f32;

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());Run

[−]

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

use std::f32;

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());Run

[−]

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;
use std::f32;

let num = 12.4_f32;
let inf = f32::INFINITY;

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

[−]

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

let f = 3.99_f32;
let g = 3.0_f32;

assert_eq!(f.floor(), 3.0);
assert_eq!(g.floor(), 3.0);Run

[−]

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

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

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

[−]

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

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

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

[−]

Returns the integer part of a number.

let f = 3.3_f32;
let g = -3.7_f32;

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

[−]

Returns the fractional part of a number.

use std::f32;

let x = 3.5_f32;
let y = -3.5_f32;
let abs_difference_x = (x.fract() - 0.5).abs();
let abs_difference_y = (y.fract() - (-0.5)).abs();

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

[−]

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

use std::f32;

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());Run

[−]

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
use std::f32;

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());Run

[−]

Returns true if and only 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());Run

[−]

Returns true if and only 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());Run

[−]

Fused multiply-add. Computes (self * a) + b with only one rounding error. This produces a more accurate result with better performance than a separate multiplication operation followed by an add.

use std::f32;

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);Run

[−]

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

use std::f32;

let x = 2.0_f32;
let abs_difference = (x.recip() - (1.0/x)).abs();

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

[−]

Raises a number to an integer power.

Using this function is generally faster than using powf

use std::f32;

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

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

[−]

Raises a number to a floating point power.

use std::f32;

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

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

[−]

Takes the square root of a number.

Returns NaN if self is a negative number.

use std::f32;

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());Run

[−]

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

use std::f32;

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);Run

[−]

Returns 2^(self).

use std::f32;

let f = 2.0f32;

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

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

[−]

Returns the natural logarithm of the number.

use std::f32;

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);Run

[−]

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.

use std::f32;

let five = 5.0f32;

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

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

[−]

Returns the base 2 logarithm of the number.

use std::f32;

let two = 2.0f32;

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

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

[−]

Returns the base 10 logarithm of the number.

use std::f32;

let ten = 10.0f32;

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

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

[−]

Converts radians to degrees.

use std::f32::{self, consts};

let angle = consts::PI;

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

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

[−]

Converts degrees to radians.

use std::f32::{self, consts};

let angle = 180.0f32;

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

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

[−]

Returns the maximum of the two numbers.

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

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

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

[−]

Returns the minimum of the two numbers.

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

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

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

[−]

Deprecated since 1.10.0

: you probably meant (self - other).abs(): this operation is (self - other).max(0.0) (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
use std::f32;

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);Run

[−]

Takes the cubic root of a number.

use std::f32;

let x = 8.0f32;

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

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

[−]

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

use std::f32;

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);Run

[−]

Computes the sine of a number (in radians).

use std::f32;

let x = f32::consts::PI/2.0;

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

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

[−]

Computes the cosine of a number (in radians).

use std::f32;

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

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

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

[−]

Computes the tangent of a number (in radians).

use std::f32;

let x = f32::consts::PI / 4.0;
let abs_difference = (x.tan() - 1.0).abs();

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

[−]

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].

use std::f32;

let f = f32::consts::PI / 2.0;

// asin(sin(pi/2))
let abs_difference = (f.sin().asin() - f32::consts::PI / 2.0).abs();

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

[−]

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].

use std::f32;

let f = f32::consts::PI / 4.0;

// acos(cos(pi/4))
let abs_difference = (f.cos().acos() - f32::consts::PI / 4.0).abs();

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

[−]

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

use std::f32;

let f = 1.0f32;

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

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

[−]

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)
use std::f32;

let pi = f32::consts::PI;
// 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) - (-pi/4.0)).abs();
let abs_difference_2 = (y2.atan2(x2) - 3.0*pi/4.0).abs();

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

[−]

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

use std::f32;

let x = f32::consts::PI/4.0;
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);Run

[−]

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

use std::f32;

let x = 6.0f32;

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

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

[−]

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

use std::f32;

let x = 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);Run

[−]

Hyperbolic sine function.

use std::f32;

let e = 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);Run

[−]

Hyperbolic cosine function.

use std::f32;

let e = 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);Run

[−]

Hyperbolic tangent function.

use std::f32;

let e = 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);Run

[−]

Inverse hyperbolic sine function.

use std::f32;

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

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

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

[−]

Inverse hyperbolic cosine function.

use std::f32;

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

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

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

[−]

Inverse hyperbolic tangent function.

use std::f32;

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

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

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

[−]

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);
Run

[−]

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 favours 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

use std::f32;
let v = f32::from_bits(0x41480000);
let difference = (v - 12.5).abs();
assert!(difference <= 1e-5);Run

Trait Implementations

impl<'a> Div<&'a f32> for f32
[src]
[+]

The resulting type after applying the / operator.

[−]

Performs the / operation.

impl Div<f32> for f32
[src]
[+]

The resulting type after applying the / operator.

[−]

Performs the / operation.

impl<'a, 'b> Div<&'a f32> for &'b f32
[src]
[+]

The resulting type after applying the / operator.

[−]

Performs the / operation.

impl<'a> Div<f32> for &'a f32
[src]
[+]

The resulting type after applying the / operator.

[−]

Performs the / operation.

impl Debug for f32
[src]
[+]

[−]

Formats the value using the given formatter. Read more

impl<'a> Add<f32> for &'a f32
[src]
[+]

The resulting type after applying the + operator.

[−]

Performs the + operation.

impl Add<f32> for f32
[src]
[+]

The resulting type after applying the + operator.

[−]

Performs the + operation.

impl<'a> Add<&'a f32> for f32
[src]
[+]

The resulting type after applying the + operator.

[−]

Performs the + operation.

impl<'a, 'b> Add<&'a f32> for &'b f32
[src]
[+]

The resulting type after applying the + operator.

[−]

Performs the + operation.

impl<'a> Sum<&'a f32> for f32
1.12.0
[src]
[+]

[−]

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

impl Sum<f32> for f32
1.12.0
[src]
[+]

[−]

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

impl DivAssign<f32> for f32
1.8.0
[src]
[+]

[−]

Performs the /= operation.

impl<'a> DivAssign<&'a f32> for f32
1.22.0
[src]
[+]

[−]

Performs the /= operation.

impl<'a> SubAssign<&'a f32> for f32
1.22.0
[src]
[+]

[−]

Performs the -= operation.

impl SubAssign<f32> for f32
1.8.0
[src]
[+]

[−]

Performs the -= operation.

impl PartialEq<f32> for f32
[src]
[+]

[−]

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

[−]

This method tests for !=.

impl From<u16> for f32
1.6.0
[src]
[+]

[−]

Performs the conversion.

impl From<u8> for f32
1.6.0
[src]
[+]

[−]

Performs the conversion.

impl From<i8> for f32
1.6.0
[src]
[+]

[−]

Performs the conversion.

impl From<i16> for f32
1.6.0
[src]
[+]

[−]

Performs the conversion.

impl LowerExp for f32
[src]
[+]

[−]

Formats the value using the given formatter.

impl FromStr for f32
[src]
[+]

The associated error which can be returned from parsing.

[−]

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.

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 Display for f32
[src]
[+]

[−]

Formats the value using the given formatter. Read more

impl<'a> Mul<&'a f32> for f32
[src]
[+]

The resulting type after applying the * operator.

[−]

Performs the * operation.

impl<'a, 'b> Mul<&'a f32> for &'b f32
[src]
[+]

The resulting type after applying the * operator.

[−]

Performs the * operation.

impl<'a> Mul<f32> for &'a f32
[src]
[+]

The resulting type after applying the * operator.

[−]

Performs the * operation.

impl Mul<f32> for f32
[src]
[+]

The resulting type after applying the * operator.

[−]

Performs the * operation.

impl<'a> Product<&'a f32> for f32
1.12.0
[src]
[+]

[−]

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

impl Product<f32> for f32
1.12.0
[src]
[+]

[−]

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

impl RemAssign<f32> for f32
1.8.0
[src]
[+]

[−]

Performs the %= operation.

impl<'a> RemAssign<&'a f32> for f32
1.22.0
[src]
[+]

[−]

Performs the %= operation.

impl MulAssign<f32> for f32
1.8.0
[src]
[+]

[−]

Performs the *= operation.

impl<'a> MulAssign<&'a f32> for f32
1.22.0
[src]
[+]

[−]

Performs the *= operation.

impl AddAssign<f32> for f32
1.8.0
[src]
[+]

[−]

Performs the += operation.

impl<'a> AddAssign<&'a f32> for f32
1.22.0
[src]
[+]

[−]

Performs the += operation.

impl UpperExp for f32
[src]
[+]

[−]

Formats the value using the given formatter.

impl<'a> Neg for &'a f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the unary - operation.

impl Neg for f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the unary - operation.

impl Default for f32
[src]
[+]

[−]

Returns the default value of 0.0

impl PartialOrd<f32> for f32
[src]
[+]

[−]

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

[−]

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

[−]

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

[−]

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

[−]

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

impl Sub<f32> for f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the - operation.

impl<'a, 'b> Sub<&'a f32> for &'b f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the - operation.

impl<'a> Sub<f32> for &'a f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the - operation.

impl<'a> Sub<&'a f32> for f32
[src]
[+]

The resulting type after applying the - operator.

[−]

Performs the - operation.

impl<'a> Rem<&'a f32> for f32
[src]
[+]

The resulting type after applying the % operator.

[−]

Performs the % operation.

impl Rem<f32> for f32
[src]
[+]

The resulting type after applying the % operator.

[−]

Performs the % operation.

impl<'a> Rem<f32> for &'a f32
[src]
[+]

The resulting type after applying the % operator.

[−]

Performs the % operation.

impl<'a, 'b> Rem<&'a f32> for &'b f32
[src]
[+]

The resulting type after applying the % operator.

[−]

Performs the % operation.