Primitive Type f64
1.0.0 ·Expand description
A 64-bit floating-point type (specifically, the “binary64” type defined in IEEE 754-2008).
This type is very similar to f32
, but has increased precision by using twice as many
bits. Please see the documentation for f32
or Wikipedia on double-precision
values for more information.
Implementations§
source§impl f64
impl f64
1.43.0 · sourcepub const MANTISSA_DIGITS: u32 = 53u32
pub const MANTISSA_DIGITS: u32 = 53u32
Number of significant digits in base 2.
1.43.0 · sourcepub const DIGITS: u32 = 15u32
pub const DIGITS: u32 = 15u32
Approximate number of significant digits in base 10.
This is the maximum x such that any decimal number with x
significant digits can be converted to f64
and back without loss.
Equal to floor(log10 2MANTISSA_DIGITS
− 1).
1.43.0 · sourcepub const EPSILON: f64 = 2.2204460492503131E-16f64
pub const EPSILON: f64 = 2.2204460492503131E-16f64
Machine epsilon value for f64
.
This is the difference between 1.0
and the next larger representable number.
Equal to 21 − MANTISSA_DIGITS
.
1.43.0 · sourcepub const MIN: f64 = -1.7976931348623157E+308f64
pub const MIN: f64 = -1.7976931348623157E+308f64
Smallest finite f64
value.
Equal to −MAX
.
1.43.0 · sourcepub const MIN_POSITIVE: f64 = 2.2250738585072014E-308f64
pub const MIN_POSITIVE: f64 = 2.2250738585072014E-308f64
Smallest positive normal f64
value.
Equal to 2MIN_EXP
− 1.
1.43.0 · sourcepub const MAX: f64 = 1.7976931348623157E+308f64
pub const MAX: f64 = 1.7976931348623157E+308f64
Largest finite f64
value.
Equal to
(1 − 2−MANTISSA_DIGITS
) 2MAX_EXP
.
1.43.0 · sourcepub const MIN_EXP: i32 = -1_021i32
pub const MIN_EXP: i32 = -1_021i32
One greater than the minimum possible normal power of 2 exponent.
If x = MIN_EXP
, then normal numbers
≥ 0.5 × 2x.
1.43.0 · sourcepub const MAX_EXP: i32 = 1_024i32
pub const MAX_EXP: i32 = 1_024i32
Maximum possible power of 2 exponent.
If x = MAX_EXP
, then normal numbers
< 1 × 2x.
1.43.0 · sourcepub const MIN_10_EXP: i32 = -307i32
pub const MIN_10_EXP: i32 = -307i32
Minimum x for which 10x is normal.
Equal to ceil(log10 MIN_POSITIVE
).
1.43.0 · sourcepub const MAX_10_EXP: i32 = 308i32
pub const MAX_10_EXP: i32 = 308i32
Maximum x for which 10x is normal.
Equal to floor(log10 MAX
).
1.43.0 · sourcepub const NAN: f64 = NaN_f64
pub const NAN: f64 = NaN_f64
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: f64 = -Inf_f64
pub const NEG_INFINITY: f64 = -Inf_f64
Negative infinity (−∞).
1.0.0 (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.
1.53.0 (const: unstable) · sourcepub fn is_subnormal(self) -> bool
pub fn is_subnormal(self) -> bool
Returns true
if the number is subnormal.
let min = f64::MIN_POSITIVE; // 2.2250738585072014e-308_f64
let max = f64::MAX;
let lower_than_min = 1.0e-308_f64;
let zero = 0.0_f64;
assert!(!min.is_subnormal());
assert!(!max.is_subnormal());
assert!(!zero.is_subnormal());
assert!(!f64::NAN.is_subnormal());
assert!(!f64::INFINITY.is_subnormal());
// Values between `0` and `min` are Subnormal.
assert!(lower_than_min.is_subnormal());
1.0.0 (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 = f64::MIN_POSITIVE; // 2.2250738585072014e-308f64
let max = f64::MAX;
let lower_than_min = 1.0e-308_f64;
let zero = 0.0f64;
assert!(min.is_normal());
assert!(max.is_normal());
assert!(!zero.is_normal());
assert!(!f64::NAN.is_normal());
assert!(!f64::INFINITY.is_normal());
// Values between `0` and `min` are Subnormal.
assert!(!lower_than_min.is_normal());
1.0.0 (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.
1.0.0 (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 or non-portable result. See the specification
of NaN bit patterns for more info. Use self.signum() == 1.0
if you need fully portable behavior (will return false
for all NaNs).
1.0.0 (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 or non-portable result. See the specification
of NaN bit patterns for more info. Use self.signum() == -1.0
if you need fully portable behavior (will return false
for all NaNs).
sourcepub const fn next_up(self) -> Self
🔬This is a nightly-only experimental API. (float_next_up_down
#91399)
pub const fn next_up(self) -> Self
float_next_up_down
#91399)Returns the least number greater than self
.
Let TINY
be the smallest representable positive f64
. 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.
sourcepub const fn next_down(self) -> Self
🔬This is a nightly-only experimental API. (float_next_up_down
#91399)
pub const fn next_down(self) -> Self
float_next_up_down
#91399)Returns the greatest number less than self
.
Let TINY
be the smallest representable positive f64
. 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.
1.0.0 · sourcepub fn to_degrees(self) -> f64
pub fn to_degrees(self) -> f64
1.0.0 · sourcepub fn to_radians(self) -> f64
pub fn to_radians(self) -> f64
1.0.0 · sourcepub fn max(self, other: f64) -> f64
pub fn max(self, other: f64) -> f64
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.
1.0.0 · sourcepub fn min(self, other: f64) -> f64
pub fn min(self, other: f64) -> f64
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.
sourcepub fn maximum(self, other: f64) -> f64
🔬This is a nightly-only experimental API. (float_minimum_maximum
#91079)
pub fn maximum(self, other: f64) -> f64
float_minimum_maximum
#91079)Returns the maximum of the two numbers, propagating NaN.
This returns NaN when either argument is NaN, as opposed to
f64::max
which only returns NaN when both arguments are NaN.
#![feature(float_minimum_maximum)]
let x = 1.0_f64;
let y = 2.0_f64;
assert_eq!(x.maximum(y), y);
assert!(x.maximum(f64::NAN).is_nan());
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 the specification of NaN bit patterns for more info.
sourcepub fn minimum(self, other: f64) -> f64
🔬This is a nightly-only experimental API. (float_minimum_maximum
#91079)
pub fn minimum(self, other: f64) -> f64
float_minimum_maximum
#91079)Returns the minimum of the two numbers, propagating NaN.
This returns NaN when either argument is NaN, as opposed to
f64::min
which only returns NaN when both arguments are NaN.
#![feature(float_minimum_maximum)]
let x = 1.0_f64;
let y = 2.0_f64;
assert_eq!(x.minimum(y), x);
assert!(x.minimum(f64::NAN).is_nan());
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 the specification of NaN bit patterns for more info.
sourcepub fn midpoint(self, other: f64) -> f64
🔬This is a nightly-only experimental API. (num_midpoint
#110840)
pub fn midpoint(self, other: f64) -> f64
num_midpoint
#110840)Calculates the middle point of self
and rhs
.
This returns NaN when either argument is NaN or if a combination of +inf and -inf is provided as arguments.
§Examples
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_f64;
let rounded = unsafe { value.to_int_unchecked::<u16>() };
assert_eq!(rounded, 4);
let value = -128.9_f64;
let rounded = unsafe { value.to_int_unchecked::<i8>() };
assert_eq!(rounded, i8::MIN);
§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) · sourcepub fn to_bits(self) -> u64
pub fn to_bits(self) -> u64
Raw transmutation to u64
.
This is currently identical to transmute::<f64, u64>(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
1.20.0 (const: unstable) · sourcepub fn from_bits(v: u64) -> Self
pub fn from_bits(v: u64) -> Self
Raw transmutation from u64
.
This is currently identical to transmute::<u64, f64>(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 signaling-ness (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
1.40.0 (const: unstable) · sourcepub fn to_be_bytes(self) -> [u8; 8]
pub fn to_be_bytes(self) -> [u8; 8]
1.40.0 (const: unstable) · sourcepub fn to_le_bytes(self) -> [u8; 8]
pub fn to_le_bytes(self) -> [u8; 8]
1.40.0 (const: unstable) · sourcepub fn to_ne_bytes(self) -> [u8; 8]
pub fn to_ne_bytes(self) -> [u8; 8]
Returns 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
1.40.0 (const: unstable) · sourcepub fn from_be_bytes(bytes: [u8; 8]) -> Self
pub fn from_be_bytes(bytes: [u8; 8]) -> Self
1.40.0 (const: unstable) · sourcepub fn from_le_bytes(bytes: [u8; 8]) -> Self
pub fn from_le_bytes(bytes: [u8; 8]) -> Self
1.40.0 (const: unstable) · sourcepub fn from_ne_bytes(bytes: [u8; 8]) -> Self
pub fn from_ne_bytes(bytes: [u8; 8]) -> Self
Creates 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
1.62.0 · sourcepub fn total_cmp(&self, other: &Self) -> Ordering
pub fn total_cmp(&self, other: &Self) -> Ordering
Returns 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 f64
. 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: f64,
}
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: f64::INFINITY },
GoodBoy { name: "Abs. Unit".to_owned(), weight: f64::NAN },
GoodBoy { name: "Floaty".to_owned(), weight: -5.0 },
];
bois.sort_by(|a, b| a.weight.total_cmp(&b.weight));
// `f64::NAN` could be positive or negative, which will affect the sort order.
if f64::NAN.is_sign_negative() {
assert!(bois.into_iter().map(|b| b.weight)
.zip([f64::NAN, -5.0, 0.1, 10.0, 99.0, f64::INFINITY].iter())
.all(|(a, b)| a.to_bits() == b.to_bits()))
} else {
assert!(bois.into_iter().map(|b| b.weight)
.zip([-5.0, 0.1, 10.0, 99.0, f64::INFINITY, f64::NAN].iter())
.all(|(a, b)| a.to_bits() == b.to_bits()))
}
1.50.0 · sourcepub fn clamp(self, min: f64, max: f64) -> f64
pub fn clamp(self, min: f64, max: f64) -> f64
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
Trait Implementations§
1.22.0 · source§impl AddAssign<&f64> for f64
impl AddAssign<&f64> for f64
source§fn add_assign(&mut self, other: &f64)
fn add_assign(&mut self, other: &f64)
+=
operation. Read more1.8.0 · source§impl AddAssign for f64
impl AddAssign for f64
source§fn add_assign(&mut self, other: f64)
fn add_assign(&mut self, other: f64)
+=
operation. Read more1.22.0 · source§impl DivAssign<&f64> for f64
impl DivAssign<&f64> for f64
source§fn div_assign(&mut self, other: &f64)
fn div_assign(&mut self, other: &f64)
/=
operation. Read more1.8.0 · source§impl DivAssign for f64
impl DivAssign for f64
source§fn div_assign(&mut self, other: f64)
fn div_assign(&mut self, other: f64)
/=
operation. Read more1.0.0 · source§impl FromStr for f64
impl FromStr for f64
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+ ) 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).
source§type Err = ParseFloatError
type Err = ParseFloatError
1.22.0 · source§impl MulAssign<&f64> for f64
impl MulAssign<&f64> for f64
source§fn mul_assign(&mut self, other: &f64)
fn mul_assign(&mut self, other: &f64)
*=
operation. Read more1.8.0 · source§impl MulAssign for f64
impl MulAssign for f64
source§fn mul_assign(&mut self, other: f64)
fn mul_assign(&mut self, other: f64)
*=
operation. Read more1.0.0 · source§impl PartialOrd for f64
impl PartialOrd for f64
1.0.0 · source§impl Rem for f64
impl Rem for f64
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
1.22.0 · source§impl RemAssign<&f64> for f64
impl RemAssign<&f64> for f64
source§fn rem_assign(&mut self, other: &f64)
fn rem_assign(&mut self, other: &f64)
%=
operation. Read more1.8.0 · source§impl RemAssign for f64
impl RemAssign for f64
source§fn rem_assign(&mut self, other: f64)
fn rem_assign(&mut self, other: f64)
%=
operation. Read moresource§impl SimdElement for f64
impl SimdElement for f64
1.22.0 · source§impl SubAssign<&f64> for f64
impl SubAssign<&f64> for f64
source§fn sub_assign(&mut self, other: &f64)
fn sub_assign(&mut self, other: &f64)
-=
operation. Read more1.8.0 · source§impl SubAssign for f64
impl SubAssign for f64
source§fn sub_assign(&mut self, other: f64)
fn sub_assign(&mut self, other: f64)
-=
operation. Read more