## Expand description

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.

## Implementations

source### impl f32

### impl f32

1.43.0 · source#### pub const MANTISSA_DIGITS: u32

#### pub const MANTISSA_DIGITS: u32

Number of significant digits in base 2.

1.43.0 · source#### pub const EPSILON: f32

#### pub const EPSILON: f32

Machine epsilon value for `f32`

.

This is the difference between `1.0`

and the next larger representable number.

1.43.0 · source#### pub const MIN_POSITIVE: f32

#### pub const MIN_POSITIVE: f32

Smallest positive normal `f32`

value.

1.43.0 · source#### pub const MIN_EXP: i32

#### pub const MIN_EXP: i32

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

1.43.0 · source#### pub const MIN_10_EXP: i32

#### pub const MIN_10_EXP: i32

Minimum possible normal power of 10 exponent.

1.43.0 · source#### pub const MAX_10_EXP: i32

#### pub const MAX_10_EXP: i32

Maximum possible power of 10 exponent.

1.43.0 · source#### pub const NEG_INFINITY: f32

#### pub const NEG_INFINITY: f32

Negative infinity (−∞).

const: unstable · source#### pub fn is_nan(self) -> bool

#### 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());
```

Runconst: unstable · source#### pub fn is_infinite(self) -> bool

#### 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());
```

Runconst: unstable · source#### pub fn is_finite(self) -> bool

#### 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());
```

Run1.53.0 (const: unstable) · source#### pub fn is_subnormal(self) -> bool

#### pub fn is_subnormal(self) -> bool

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());
```

Runconst: unstable · source#### pub fn is_normal(self) -> bool

#### 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());
```

Runconst: unstable · source#### pub fn classify(self) -> FpCategory

#### 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);
```

Runconst: unstable · source#### pub fn is_sign_positive(self) -> bool

#### pub fn is_sign_positive(self) -> bool

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());
```

Runconst: unstable · source#### pub fn is_sign_negative(self) -> bool

#### pub fn is_sign_negative(self) -> bool

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());
```

Runsource#### pub fn recip(self) -> f32

#### 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);
```

Run1.7.0 · source#### pub fn to_degrees(self) -> f32

#### 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);
```

Run1.7.0 · source#### pub fn to_radians(self) -> f32

#### 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);
```

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

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

Returns the maximum of the two numbers.

Follows the IEEE-754 2008 semantics for maxNum, except for handling of signaling NaNs. This matches the behavior of libm’s fmax.

```
let x = 1.0f32;
let y = 2.0f32;
assert_eq!(x.max(y), y);
```

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

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

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

Returns the minimum of the two numbers.

Follows the IEEE-754 2008 semantics for minNum, except for handling of signaling NaNs. This matches the behavior of libm’s fmin.

```
let x = 1.0f32;
let y = 2.0f32;
assert_eq!(x.min(y), x);
```

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

source#### pub fn maximum(self, other: f32) -> f32

#### pub fn maximum(self, other: f32) -> f32

Returns the maximum of the two numbers, propagating NaNs.

This returns NaN when *either* argument is NaN, as opposed to
`f32::max`

which only returns NaN when *both* arguments are NaN.

```
#![feature(float_minimum_maximum)]
let x = 1.0f32;
let y = 2.0f32;
assert_eq!(x.maximum(y), y);
assert!(x.maximum(f32::NAN).is_nan());
```

RunIf one of the arguments is NaN, then NaN is returned. Otherwise this returns the greater of the two numbers. For this operation, -0.0 is considered to be less than +0.0. Note that this follows the semantics specified in IEEE 754-2019.

source#### pub fn minimum(self, other: f32) -> f32

#### pub fn minimum(self, other: f32) -> f32

Returns the minimum of the two numbers, propagating NaNs.

This returns NaN when *either* argument is NaN, as opposed to
`f32::min`

which only returns NaN when *both* arguments are NaN.

```
#![feature(float_minimum_maximum)]
let x = 1.0f32;
let y = 2.0f32;
assert_eq!(x.minimum(y), x);
assert!(x.minimum(f32::NAN).is_nan());
```

RunIf one of the arguments is NaN, then NaN is returned. Otherwise this returns the lesser of the two numbers. For this operation, -0.0 is considered to be less than +0.0. Note that this follows the semantics specified in IEEE 754-2019.

1.44.0 · source#### pub unsafe fn to_int_unchecked<Int>(self) -> Int where

Self: FloatToInt<Int>,

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

Self: 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);
```

Run##### Safety

The value must:

- Not be
`NaN`

- Not be infinite
- Be representable in the return type
`Int`

, after truncating off its fractional part

1.20.0 (const: unstable) · source#### pub fn to_bits(self) -> u32

#### 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);
```

Run1.20.0 (const: unstable) · source#### pub fn from_bits(v: u32) -> Self

#### pub fn from_bits(v: u32) -> Self

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);
```

Run1.40.0 (const: unstable) · source#### pub fn to_ne_bytes(self) -> [u8; 4]

#### 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]
}
);
```

Run1.40.0 (const: unstable) · source#### pub fn from_ne_bytes(bytes: [u8; 4]) -> Self

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

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);
```

Run1.62.0 · source#### pub fn total_cmp(&self, other: &Self) -> Ordering

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

Return the ordering between `self`

and `other`

.

Unlike the standard partial comparison between floating point numbers,
this comparison always produces an ordering in accordance to
the `totalOrder`

predicate as defined in the IEEE 754 (2008 revision)
floating point standard. The values are ordered in the following sequence:

- negative quiet NaN
- negative signaling NaN
- negative infinity
- negative numbers
- negative subnormal numbers
- negative zero
- positive zero
- positive subnormal numbers
- positive numbers
- positive infinity
- positive signaling NaN
- positive quiet NaN.

The ordering established by this function does not always agree with the
`PartialOrd`

and `PartialEq`

implementations of `f32`

. For example,
they consider negative and positive zero equal, while `total_cmp`

doesn’t.

The interpretation of the signaling NaN bit follows the definition in the IEEE 754 standard, which may not match the interpretation by some of the older, non-conformant (e.g. MIPS) hardware implementations.

##### Example

```
struct GoodBoy {
name: String,
weight: f32,
}
let mut bois = vec![
GoodBoy { name: "Pucci".to_owned(), weight: 0.1 },
GoodBoy { name: "Woofer".to_owned(), weight: 99.0 },
GoodBoy { name: "Yapper".to_owned(), weight: 10.0 },
GoodBoy { name: "Chonk".to_owned(), weight: f32::INFINITY },
GoodBoy { name: "Abs. Unit".to_owned(), weight: f32::NAN },
GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
];
bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
```

Run1.50.0 · source#### pub fn clamp(self, min: f32, max: f32) -> f32

#### 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());
```

Run## Trait Implementations

1.22.0 (const: unstable) · source### impl AddAssign<&'_ f32> for f32

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

const: unstable · source#### fn add_assign(&mut self, other: &f32)

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

Performs the `+=`

operation. Read more

1.8.0 (const: unstable) · source### impl AddAssign<f32> for f32

### impl AddAssign<f32> for f32

const: unstable · source#### fn add_assign(&mut self, other: f32)

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

Performs the `+=`

operation. Read more

1.22.0 (const: unstable) · source### impl DivAssign<&'_ f32> for f32

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

const: unstable · source#### fn div_assign(&mut self, other: &f32)

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

Performs the `/=`

operation. Read more

1.8.0 (const: unstable) · source### impl DivAssign<f32> for f32

### impl DivAssign<f32> for f32

const: unstable · source#### fn div_assign(&mut self, other: f32)

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

Performs the `/=`

operation. Read more

source### impl FromStr for f32

### impl FromStr for f32

source#### fn from_str(src: &str) -> Result<Self, ParseFloatError>

#### fn from_str(src: &str) -> Result<Self, 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’, ‘+infinity’, ‘NaN’

Note that alphabetical characters are not case-sensitive.

Leading and trailing whitespace represent an error.

##### Grammar

All strings that adhere to the following EBNF grammar when
lowercased will result in an `Ok`

being returned:

```
Float ::= Sign? ( 'inf' | 'infinity' | 'nan' | Number )
Number ::= ( Digit+ |
'.' Digit* |
Digit+ '.' Digit* |
Digit* '.' Digit+ ) Exp?
Exp ::= 'e' 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

#### type Err = ParseFloatError

The associated error which can be returned from parsing.

1.22.0 (const: unstable) · source### impl MulAssign<&'_ f32> for f32

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

const: unstable · source#### fn mul_assign(&mut self, other: &f32)

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

Performs the `*=`

operation. Read more

1.8.0 (const: unstable) · source### impl MulAssign<f32> for f32

### impl MulAssign<f32> for f32

const: unstable · source#### fn mul_assign(&mut self, other: f32)

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

Performs the `*=`

operation. Read more

source### impl PartialOrd<f32> for f32

### impl PartialOrd<f32> for f32

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

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

This method returns an ordering between `self`

and `other`

values if one exists. Read more

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

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

This method tests less than (for `self`

and `other`

) and is used by the `<`

operator. Read more

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

#### 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

const: unstable · source### impl Rem<f32> for f32

### 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);
```

Run1.22.0 (const: unstable) · source### impl RemAssign<&'_ f32> for f32

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

const: unstable · source#### fn rem_assign(&mut self, other: &f32)

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

Performs the `%=`

operation. Read more

1.8.0 (const: unstable) · source### impl RemAssign<f32> for f32

### impl RemAssign<f32> for f32

const: unstable · source#### fn rem_assign(&mut self, other: f32)

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

Performs the `%=`

operation. Read more

source### impl SimdElement for f32

### impl SimdElement for f32

1.22.0 (const: unstable) · source### impl SubAssign<&'_ f32> for f32

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

const: unstable · source#### fn sub_assign(&mut self, other: &f32)

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

Performs the `-=`

operation. Read more

1.8.0 (const: unstable) · source### impl SubAssign<f32> for f32

### impl SubAssign<f32> for f32

const: unstable · source#### fn sub_assign(&mut self, other: f32)

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

Performs the `-=`

operation. Read more