pub type c_float = f32;
Expand description
Equivalent to C’s float
type.
This type will almost always be f32
, which is guaranteed to be an IEEE 754 single-precision float in Rust. That said, the standard technically only guarantees that it be a floating-point number, and it may have less precision than f32
or not follow the IEEE-754 standard at all.
Implementations§
source§impl f32
impl f32
1.43.0 · sourcepub const MANTISSA_DIGITS: u32 = 24u32
pub const MANTISSA_DIGITS: u32 = 24u32
Number of significant digits in base 2.
1.43.0 · sourcepub const EPSILON: f32 = 1.1920929E-7f32
pub const EPSILON: f32 = 1.1920929E-7f32
Machine epsilon value for f32
.
This is the difference between 1.0
and the next larger representable number.
1.43.0 · sourcepub const MIN_POSITIVE: f32 = 1.17549435E-38f32
pub const MIN_POSITIVE: f32 = 1.17549435E-38f32
Smallest positive normal f32
value.
1.43.0 · sourcepub const MIN_EXP: i32 = -125i32
pub const MIN_EXP: i32 = -125i32
One greater than the minimum possible normal power of 2 exponent.
1.43.0 · sourcepub const MIN_10_EXP: i32 = -37i32
pub const MIN_10_EXP: i32 = -37i32
Minimum possible normal power of 10 exponent.
1.43.0 · sourcepub const MAX_10_EXP: i32 = 38i32
pub const MAX_10_EXP: i32 = 38i32
Maximum possible power of 10 exponent.
1.43.0 · sourcepub const NAN: f32 = NaNf32
pub const NAN: f32 = NaNf32
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.
1.43.0 · sourcepub const NEG_INFINITY: f32 = -Inff32
pub const NEG_INFINITY: f32 = -Inff32
Negative infinity (−∞).
1.0.0 (const: unstable) · sourcepub 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());
Run1.0.0 (const: unstable) · sourcepub 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());
Run1.0.0 (const: unstable) · sourcepub 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) · sourcepub 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());
Run1.0.0 (const: unstable) · sourcepub 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());
Run1.0.0 (const: unstable) · sourcepub 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);
Run1.0.0 (const: unstable) · sourcepub fn is_sign_positive(self) -> bool
pub fn is_sign_positive(self) -> bool
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());
Run1.0.0 (const: unstable) · sourcepub fn is_sign_negative(self) -> bool
pub fn is_sign_negative(self) -> bool
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());
Runconst: unstable · sourcepub fn next_up(self) -> Self
🔬This is a nightly-only experimental API. (float_next_up_down
#91399)
pub fn next_up(self) -> Self
float_next_up_down
#91399)Returns the least number greater than self
.
Let TINY
be the smallest representable positive f32
. Then,
- if
self.is_nan()
, this returnsself
; - if
self
isNEG_INFINITY
, this returnsMIN
; - if
self
is-TINY
, this returns -0.0; - if
self
is -0.0 or +0.0, this returnsTINY
; - if
self
isMAX
orINFINITY
, this returnsINFINITY
; - otherwise the unique least value greater than
self
is returned.
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);
Runconst: unstable · sourcepub fn next_down(self) -> Self
🔬This is a nightly-only experimental API. (float_next_up_down
#91399)
pub fn next_down(self) -> Self
float_next_up_down
#91399)Returns the greatest number less than self
.
Let TINY
be the smallest representable positive f32
. Then,
- if
self.is_nan()
, this returnsself
; - if
self
isINFINITY
, this returnsMAX
; - if
self
isTINY
, this returns 0.0; - if
self
is -0.0 or +0.0, this returns-TINY
; - if
self
isMIN
orNEG_INFINITY
, this returnsNEG_INFINITY
; - otherwise the unique greatest value less than
self
is returned.
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);
Run1.0.0 · sourcepub 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 · sourcepub 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 · sourcepub 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);
Run1.0.0 · sourcepub fn max(self, other: f32) -> f32
pub fn max(self, other: f32) -> f32
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);
Run1.0.0 · sourcepub fn min(self, other: f32) -> f32
pub fn min(self, other: f32) -> f32
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);
Runsourcepub fn maximum(self, other: f32) -> f32
🔬This is a nightly-only experimental API. (float_minimum_maximum
#91079)
pub fn maximum(self, other: f32) -> f32
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());
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.
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.
sourcepub fn minimum(self, other: f32) -> f32
🔬This is a nightly-only experimental API. (float_minimum_maximum
#91079)
pub fn minimum(self, other: f32) -> f32
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());
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.
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.
sourcepub fn midpoint(self, other: f32) -> f32
🔬This is a nightly-only experimental API. (num_midpoint
#110840)
pub fn midpoint(self, other: f32) -> f32
num_midpoint
#110840)1.44.0 · sourcepub unsafe fn to_int_unchecked<Int>(self) -> Intwhere
Self: FloatToInt<Int>,
pub unsafe fn to_int_unchecked<Int>(self) -> Intwhere 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);
RunSafety
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) · sourcepub 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) · sourcepub 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) · sourcepub fn to_be_bytes(self) -> [u8; 4]
pub fn to_be_bytes(self) -> [u8; 4]
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]);
Run1.40.0 (const: unstable) · sourcepub fn to_le_bytes(self) -> [u8; 4]
pub fn to_le_bytes(self) -> [u8; 4]
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]);
Run1.40.0 (const: unstable) · sourcepub 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.
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]
}
);
Run1.40.0 (const: unstable) · sourcepub fn from_be_bytes(bytes: [u8; 4]) -> Self
pub fn from_be_bytes(bytes: [u8; 4]) -> Self
1.40.0 (const: unstable) · sourcepub fn from_le_bytes(bytes: [u8; 4]) -> Self
pub fn from_le_bytes(bytes: [u8; 4]) -> Self
1.40.0 (const: unstable) · sourcepub 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.
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);
Run1.62.0 · sourcepub 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 · sourcepub 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());
RunTrait Implementations§
1.22.0 · source§impl AddAssign<&f32> for f32
impl AddAssign<&f32> for f32
source§fn add_assign(&mut self, other: &f32)
fn add_assign(&mut self, other: &f32)
+=
operation. Read more1.8.0 · source§impl AddAssign<f32> for f32
impl AddAssign<f32> for f32
source§fn add_assign(&mut self, other: f32)
fn add_assign(&mut self, other: f32)
+=
operation. Read more1.22.0 · source§impl DivAssign<&f32> for f32
impl DivAssign<&f32> for f32
source§fn div_assign(&mut self, other: &f32)
fn div_assign(&mut self, other: &f32)
/=
operation. Read more1.8.0 · source§impl DivAssign<f32> for f32
impl DivAssign<f32> for f32
source§fn div_assign(&mut self, other: f32)
fn div_assign(&mut self, other: f32)
/=
operation. Read more1.22.0 · source§impl MulAssign<&f32> for f32
impl MulAssign<&f32> for f32
source§fn mul_assign(&mut self, other: &f32)
fn mul_assign(&mut self, other: &f32)
*=
operation. Read more1.8.0 · source§impl MulAssign<f32> for f32
impl MulAssign<f32> for f32
source§fn mul_assign(&mut self, other: f32)
fn mul_assign(&mut self, other: f32)
*=
operation. Read more1.0.0 · source§impl PartialOrd<f32> for f32
impl PartialOrd<f32> for f32
source§fn le(&self, other: &f32) -> bool
fn le(&self, other: &f32) -> bool
self
and other
) and is used by the <=
operator. Read more1.0.0 · 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 · source§impl RemAssign<&f32> for f32
impl RemAssign<&f32> for f32
source§fn rem_assign(&mut self, other: &f32)
fn rem_assign(&mut self, other: &f32)
%=
operation. Read more1.8.0 · source§impl RemAssign<f32> for f32
impl RemAssign<f32> for f32
source§fn rem_assign(&mut self, other: f32)
fn rem_assign(&mut self, other: f32)
%=
operation. Read moresource§impl SimdElement for f32
impl SimdElement for f32
1.22.0 · source§impl SubAssign<&f32> for f32
impl SubAssign<&f32> for f32
source§fn sub_assign(&mut self, other: &f32)
fn sub_assign(&mut self, other: &f32)
-=
operation. Read more1.8.0 · source§impl SubAssign<f32> for f32
impl SubAssign<f32> for f32
source§fn sub_assign(&mut self, other: f32)
fn sub_assign(&mut self, other: f32)
-=
operation. Read more