# Primitive Type f321.0.0[−]

## 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

Number of significant digits in base 2.

Machine epsilon value for `f32`

.

This is the difference between `1.0`

and the next larger representable number.

Smallest positive normal `f32`

value.

Minimum possible normal power of 10 exponent.

Maximum possible power of 10 exponent.

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());
```

RunReturns `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());
```

RunReturns `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());
```

RunReturns `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());
```

RunReturns `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());
```

RunReturns 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);
```

RunReturns `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());
```

RunReturns `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());
```

RunTakes 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);
```

RunConverts radians to degrees.

```
let angle = std::f32::consts::PI;
let abs_difference = (angle.to_degrees() - 180.0).abs();
assert!(abs_difference <= f32::EPSILON);
```

RunConverts degrees to radians.

```
let angle = 180.0f32;
let abs_difference = (angle.to_radians() - std::f32::consts::PI).abs();
assert!(abs_difference <= f32::EPSILON);
```

RunReturns the maximum of the two numbers.

```
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.

Returns the minimum of the two numbers.

```
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.

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

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);
```

RunRaw 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);
```

RunReturn 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]
}
);
```

RunCreate 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);
```

RunReturns 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));
```

RunRestrict 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

Performs the `+=`

operation. Read more

Performs the `+=`

operation. Read more

Performs the `/=`

operation. Read more

Performs the `/=`

operation. Read more

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

#### type Err = ParseFloatError

The associated error which can be returned from parsing.

Performs the `*=`

operation. Read more

Performs the `*=`

operation. Read more

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

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);
```

RunPerforms the `%=`

operation. Read more

Performs the `%=`

operation. Read more

Performs the `-=`

operation. Read more

Performs the `-=`

operation. Read more