# Primitive Type f32

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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! This is the reason `f32` doesn’t implement the `Eq` trait.
• It is also neither smaller nor greater than any float, making it impossible to sort by the default comparison operation, which is the reason `f32` doesn’t implement the `Ord` trait.
• It is also considered infectious as almost all calculations where one of the operands is NaN will also result in NaN. The explanations on this page only explicitly document behavior on NaN operands if this default is deviated from.
• Lastly, there are multiple bit patterns that are considered NaN. Rust does not currently guarantee that the bit patterns of NaN are preserved over arithmetic operations, and they are not guaranteed to be portable or even fully deterministic! This means that there may be some surprising results upon inspecting the bit patterns, as the same calculations might produce NaNs with different bit patterns.

When the number resulting from a primitive operation (addition, subtraction, multiplication, or division) on this type is not exactly representable as `f32`, it is rounded according to the roundTiesToEven direction defined in IEEE 754-2008. That means:

• The result is the representable value closest to the true value, if there is a unique closest representable value.
• If the true value is exactly half-way between two representable values, the result is the one with an even least-significant binary digit.
• If the true value’s magnitude is ≥ `f32::MAX` + 2(`f32::MAX_EXP``f32::MANTISSA_DIGITS` − 1), the result is ∞ or −∞ (preserving the true value’s sign).

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

## Implementations

The radix or base of the internal representation of `f32`.

Number of significant digits in base 2.

Approximate number of significant digits in base 10.

Machine epsilon value for `f32`.

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

Smallest finite `f32` value.

Smallest positive normal `f32` value.

Largest finite `f32` value.

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

Maximum possible power of 2 exponent.

Minimum possible normal power of 10 exponent.

Maximum possible power of 10 exponent.

Not a Number (NaN).

Note that IEEE 754 doesn’t define just a single NaN value; a plethora of bit patterns are considered to be NaN. Furthermore, the standard makes a difference between a “signaling” and a “quiet” NaN, and allows inspecting its “payload” (the unspecified bits in the bit pattern). This constant isn’t guaranteed to equal to any specific NaN bitpattern, and the stability of its representation over Rust versions and target platforms isn’t guaranteed.

Infinity (∞).

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());``````
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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());``````
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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());``````
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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());``````
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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());``````
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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);``````
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Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with positive sign bit and positive infinity. Note that IEEE 754 doesn’t assign any meaning to the sign bit in case of a NaN, and as Rust doesn’t guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the result of `is_sign_positive` on a NaN might produce an unexpected result in some cases. See explanation of NaN as a special value for more info.

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

assert!(f.is_sign_positive());
assert!(!g.is_sign_positive());``````
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Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with negative sign bit and negative infinity. Note that IEEE 754 doesn’t assign any meaning to the sign bit in case of a NaN, and as Rust doesn’t guarantee that the bit pattern of NaNs are conserved over arithmetic operations, the result of `is_sign_negative` on a NaN might produce an unexpected result in some cases. See explanation of NaN as a special value for more info.

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

assert!(!f.is_sign_negative());
assert!(g.is_sign_negative());``````
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🔬This is a nightly-only experimental API. (`float_next_up_down` #91399)

Returns the least number greater than `self`.

Let `TINY` be the smallest representable positive `f32`. Then,

The identity `x.next_up() == -(-x).next_down()` holds for all non-NaN `x`. When `x` is finite `x == x.next_up().next_down()` also holds.

``````#![feature(float_next_up_down)]
// f32::EPSILON is the difference between 1.0 and the next number up.
assert_eq!(1.0f32.next_up(), 1.0 + f32::EPSILON);
// But not for most numbers.
assert!(0.1f32.next_up() < 0.1 + f32::EPSILON);
assert_eq!(16777216f32.next_up(), 16777218.0);``````
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🔬This is a nightly-only experimental API. (`float_next_up_down` #91399)

Returns the greatest number less than `self`.

Let `TINY` be the smallest representable positive `f32`. Then,

The identity `x.next_down() == -(-x).next_up()` holds for all non-NaN `x`. When `x` is finite `x == x.next_down().next_up()` also holds.

``````#![feature(float_next_up_down)]
let x = 1.0f32;
// Clamp value into range [0, 1).
let clamped = x.clamp(0.0, 1.0f32.next_down());
assert!(clamped < 1.0);
assert_eq!(clamped.next_up(), 1.0);``````
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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);``````
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``````let angle = std::f32::consts::PI;

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

assert!(abs_difference <= f32::EPSILON);``````
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``````let angle = 180.0f32;

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

assert!(abs_difference <= f32::EPSILON);``````
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Returns the maximum of the two numbers, ignoring NaN.

If one of the arguments is NaN, then the other argument is returned. This follows the IEEE 754-2008 semantics for maxNum, except for handling of signaling NaNs; this function handles all NaNs the same way and avoids maxNum’s problems with associativity. This also matches the behavior of libm’s fmax.

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

assert_eq!(x.max(y), y);``````
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Returns the minimum of the two numbers, ignoring NaN.

If one of the arguments is NaN, then the other argument is returned. This follows the IEEE 754-2008 semantics for minNum, except for handling of signaling NaNs; this function handles all NaNs the same way and avoids minNum’s problems with associativity. This also matches the behavior of libm’s fmin.

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

assert_eq!(x.min(y), x);``````
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🔬This is a nightly-only experimental API. (`float_minimum_maximum` #91079)

Returns the maximum of the two numbers, propagating NaN.

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());``````
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If 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.

Also note that “propagation” of NaNs here doesn’t necessarily mean that the bitpattern of a NaN operand is conserved; see explanation of NaN as a special value for more info.

🔬This is a nightly-only experimental API. (`float_minimum_maximum` #91079)

Returns the minimum of the two numbers, propagating NaN.

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());``````
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If 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.

Also note that “propagation” of NaNs here doesn’t necessarily mean that the bitpattern of a NaN operand is conserved; see explanation of NaN as a special value for more info.

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

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

##### Examples
``````let bytes = 12.5f32.to_be_bytes();
assert_eq!(bytes, [0x41, 0x48, 0x00, 0x00]);``````
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Return the memory representation of this floating point number as a byte array in little-endian byte order.

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

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

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

##### 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]
}
);``````
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Create a floating point value from its representation as a byte array in big endian.

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

##### Examples
``````let value = f32::from_be_bytes([0x41, 0x48, 0x00, 0x00]);
assert_eq!(value, 12.5);``````
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Create a floating point value from its representation as a byte array in little endian.

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

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

See `from_bits` for some discussion of the portability of this operation (there are almost no issues).

##### 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);``````
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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));``````
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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());``````
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## Trait Implementations

The resulting type after applying the `+` operator.
Performs the `+` operation. Read more
The resulting type after applying the `+` operator.
Performs the `+` operation. Read more
The resulting type after applying the `+` operator.
Performs the `+` operation. Read more
The resulting type after applying the `+` operator.
Performs the `+` operation. Read more
Performs the `+=` operation. Read more
Performs the `+=` operation. Read more
Returns a copy of the value. Read more
Performs copy-assignment from `source`. Read more
Formats the value using the given formatter. Read more

Returns the default value of `0.0`

Formats the value using the given formatter. Read more
The resulting type after applying the `/` operator.
Performs the `/` operation. Read more
The resulting type after applying the `/` operator.
Performs the `/` operation. Read more
The resulting type after applying the `/` operator.
Performs the `/` operation. Read more
The resulting type after applying the `/` operator.
Performs the `/` operation. Read more
Performs the `/=` operation. Read more
Performs the `/=` operation. Read more

Converts `f32` to `f64` losslessly.

Converts `i16` to `f32` losslessly.

Converts `i8` to `f32` losslessly.

Converts `u16` to `f32` losslessly.

Converts `u8` to `f32` losslessly.

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+ ) 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 closest representable floating-point number to the number represented by `src` (following the same rules for rounding as for the results of primitive operations).

The associated error which can be returned from parsing.
Formats the value using the given formatter.
The resulting type after applying the `*` operator.
Performs the `*` operation. Read more
The resulting type after applying the `*` operator.
Performs the `*` operation. Read more
The resulting type after applying the `*` operator.
Performs the `*` operation. Read more
The resulting type after applying the `*` operator.
Performs the `*` operation. Read more
Performs the `*=` operation. Read more
Performs the `*=` operation. Read more
The resulting type after applying the `-` operator.
Performs the unary `-` operation. Read more
The resulting type after applying the `-` operator.
Performs the unary `-` operation. Read more
This method tests for `self` and `other` values to be equal, and is used by `==`. Read more
This method tests for `!=`. The default implementation is almost always sufficient, and should not be overridden without very good reason. 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
This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more
Method which takes an iterator and generates `Self` from the elements by multiplying the items. Read more
Method which takes an iterator and generates `Self` from the elements by multiplying the items. Read more
The resulting type after applying the `%` operator.
Performs the `%` operation. Read more
The resulting type after applying the `%` operator.
Performs the `%` operation. Read more
The resulting type after applying the `%` operator.
Performs the `%` operation. 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);``````
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The resulting type after applying the `%` operator.
Performs the `%` operation. Read more
Performs the `%=` operation. Read more
Performs the `%=` operation. Read more
🔬This is a nightly-only experimental API. (`portable_simd` #86656)
The mask element type corresponding to this element type.
The resulting type after applying the `-` operator.
Performs the `-` operation. Read more
The resulting type after applying the `-` operator.
Performs the `-` operation. Read more
The resulting type after applying the `-` operator.
Performs the `-` operation. Read more
The resulting type after applying the `-` operator.
Performs the `-` operation. Read more
Performs the `-=` operation. Read more
Performs the `-=` operation. Read more
Method which takes an iterator and generates `Self` from the elements by “summing up” the items. Read more
Method which takes an iterator and generates `Self` from the elements by “summing up” the items. Read more
Formats the value using the given formatter.

## Blanket Implementations

Gets the `TypeId` of `self`. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.