Primitive Type bool 

The boolean type.

The bool represents a value, which could only be either true or false. If you cast a bool into an integer, true will be 1 and false will be 0.

Basic usage

bool implements various traits, such as BitAnd, BitOr, Not, etc., which allow us to perform boolean operations using &, | and !.

if requires a bool value as its conditional. assert!, which is an important macro in testing, checks whether an expression is true and panics if it isn’t.

let bool_val = true & false | false;
assert!(!bool_val);

Examples

A trivial example of the usage of bool:

let praise_the_borrow_checker = true;

// using the `if` conditional
if praise_the_borrow_checker {
    println!("oh, yeah!");
} else {
    println!("what?!!");
}

// ... or, a match pattern
match praise_the_borrow_checker {
    true => println!("keep praising!"),
    false => println!("you should praise!"),
}

Also, since bool implements the Copy trait, we don’t have to worry about the move semantics (just like the integer and float primitives).

Now an example of bool cast to integer type:

assert_eq!(true as i32, 1);
assert_eq!(false as i32, 0);

Implementations

impl bool

pub fn then_some<T>(self, t: T) -> Option<T>

Returns Some(t) if the bool is true, or None otherwise.

Arguments passed to then_some are eagerly evaluated; if you are passing the result of a function call, it is recommended to use then, which is lazily evaluated.

Examples

assert_eq!(false.then_some(0), None);
assert_eq!(true.then_some(0), Some(0));

let mut a = 0;
let mut function_with_side_effects = || { a += 1; };

true.then_some(function_with_side_effects());
false.then_some(function_with_side_effects());

// `a` is incremented twice because the value passed to `then_some` is
// evaluated eagerly.
assert_eq!(a, 2);

pub fn then<T, F: FnOnce() -> T>(self, f: F) -> Option<T>

Returns Some(f()) if the bool is true, or None otherwise.

Examples

assert_eq!(false.then(|| 0), None);
assert_eq!(true.then(|| 0), Some(0));

let mut a = 0;

true.then(|| { a += 1; });
false.then(|| { a += 1; });

// `a` is incremented once because the closure is evaluated lazily by
// `then`.
assert_eq!(a, 1);

pub fn ok_or<E>(self, err: E) -> Result<(), E>

Returns Ok(()) if the bool is true, or Err(err) otherwise.

Arguments passed to ok_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use ok_or_else, which is lazily evaluated.

Examples

assert_eq!(false.ok_or(0), Err(0));
assert_eq!(true.ok_or(0), Ok(()));

let mut a = 0;
let mut function_with_side_effects = || { a += 1; };

assert!(true.ok_or(function_with_side_effects()).is_ok());
assert!(false.ok_or(function_with_side_effects()).is_err());

// `a` is incremented twice because the value passed to `ok_or` is
// evaluated eagerly.
assert_eq!(a, 2);

pub fn ok_or_else<E, F: FnOnce() -> E>(self, f: F) -> Result<(), E>

Returns Ok(()) if the bool is true, or Err(f()) otherwise.

Examples

assert_eq!(false.ok_or_else(|| 0), Err(0));
assert_eq!(true.ok_or_else(|| 0), Ok(()));

let mut a = 0;

assert!(true.ok_or_else(|| { a += 1; }).is_ok());
assert!(false.ok_or_else(|| { a += 1; }).is_err());

// `a` is incremented once because the closure is evaluated lazily by
// `ok_or_else`.
assert_eq!(a, 1);

pub const fn toggle(&mut self)

Toggles self in-place.

• If self is true, sets self to false.
• If self is false, sets self to true.

Equivalent to value = !value.

Examples

let mut boolean = false;

boolean.toggle();
assert_eq!(boolean, true);

boolean.toggle();
assert_eq!(boolean, false);

Trait Implementations

impl AtomicPrimitive for bool

type Storage = Align1<u8>

🔬This is a nightly-only experimental API. (atomic_internals)

Temporary implementation detail.

impl BitAnd for bool

type Output = bool

The resulting type after applying the & operator.

fn bitand(self, rhs: bool) -> bool

Performs the & operation.

impl BitAnd<&bool> for bool

type Output = <bool as BitAnd>::Output

The resulting type after applying the & operator.

fn bitand(self, other: &bool) -> <bool as BitAnd<bool>>::Output

Performs the & operation.

impl BitAnd<&bool> for &bool

type Output = <bool as BitAnd>::Output

The resulting type after applying the & operator.

fn bitand(self, other: &bool) -> <bool as BitAnd<bool>>::Output

Performs the & operation.

impl<T, const N: usize> BitAnd<Mask<T, N>> for bool

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the & operator.

fn bitand(self, rhs: Mask<T, N>) -> Mask<T, N>

Performs the & operation.

impl BitAnd<bool> for &bool

type Output = <bool as BitAnd>::Output

The resulting type after applying the & operator.

fn bitand(self, other: bool) -> <bool as BitAnd<bool>>::Output

Performs the & operation.

impl<T, const N: usize> BitAnd<bool> for Mask<T, N>

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the & operator.

fn bitand(self, rhs: bool) -> Self

Performs the & operation.

impl BitAndAssign for bool

fn bitand_assign(&mut self, other: bool)

Performs the &= operation.

impl BitAndAssign<&bool> for bool

fn bitand_assign(&mut self, other: &bool)

Performs the &= operation.

impl<T, const N: usize> BitAndAssign<bool> for Mask<T, N>

where T: MaskElement,

fn bitand_assign(&mut self, rhs: bool)

Performs the &= operation.

impl BitOr for bool

type Output = bool

The resulting type after applying the | operator.

fn bitor(self, rhs: bool) -> bool

Performs the | operation.

impl BitOr<&bool> for bool

type Output = <bool as BitOr>::Output

The resulting type after applying the | operator.

fn bitor(self, other: &bool) -> <bool as BitOr<bool>>::Output

Performs the | operation.

impl BitOr<&bool> for &bool

type Output = <bool as BitOr>::Output

The resulting type after applying the | operator.

fn bitor(self, other: &bool) -> <bool as BitOr<bool>>::Output

Performs the | operation.

impl<T, const N: usize> BitOr<Mask<T, N>> for bool

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the | operator.

fn bitor(self, rhs: Mask<T, N>) -> Mask<T, N>

Performs the | operation.

impl BitOr<bool> for &bool

type Output = <bool as BitOr>::Output

The resulting type after applying the | operator.

fn bitor(self, other: bool) -> <bool as BitOr<bool>>::Output

Performs the | operation.

impl<T, const N: usize> BitOr<bool> for Mask<T, N>

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the | operator.

fn bitor(self, rhs: bool) -> Self

Performs the | operation.

impl BitOrAssign for bool

fn bitor_assign(&mut self, other: bool)

Performs the |= operation.

impl BitOrAssign<&bool> for bool

fn bitor_assign(&mut self, other: &bool)

Performs the |= operation.

impl<T, const N: usize> BitOrAssign<bool> for Mask<T, N>

where T: MaskElement,

fn bitor_assign(&mut self, rhs: bool)

Performs the |= operation.

impl BitXor for bool

type Output = bool

The resulting type after applying the ^ operator.

fn bitxor(self, other: bool) -> bool

Performs the ^ operation.

impl BitXor<&bool> for bool

type Output = <bool as BitXor>::Output

The resulting type after applying the ^ operator.

fn bitxor(self, other: &bool) -> <bool as BitXor<bool>>::Output

Performs the ^ operation.

impl BitXor<&bool> for &bool

type Output = <bool as BitXor>::Output

The resulting type after applying the ^ operator.

fn bitxor(self, other: &bool) -> <bool as BitXor<bool>>::Output

Performs the ^ operation.

impl<T, const N: usize> BitXor<Mask<T, N>> for bool

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the ^ operator.

fn bitxor(self, rhs: Mask<T, N>) -> Self::Output

Performs the ^ operation.

impl BitXor<bool> for &bool

type Output = <bool as BitXor>::Output

The resulting type after applying the ^ operator.

fn bitxor(self, other: bool) -> <bool as BitXor<bool>>::Output

Performs the ^ operation.

impl<T, const N: usize> BitXor<bool> for Mask<T, N>

where T: MaskElement,

type Output = Mask<T, N>

The resulting type after applying the ^ operator.

fn bitxor(self, rhs: bool) -> Self::Output

Performs the ^ operation.

impl BitXorAssign for bool

fn bitxor_assign(&mut self, other: bool)

Performs the ^= operation.

impl BitXorAssign<&bool> for bool

fn bitxor_assign(&mut self, other: &bool)

Performs the ^= operation.

impl<T, const N: usize> BitXorAssign<bool> for Mask<T, N>

where T: MaskElement,

fn bitxor_assign(&mut self, rhs: bool)

Performs the ^= operation.

impl Clone for bool

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

where Self:,

Performs copy-assignment from source.

impl ConstParamTy_ for bool

impl Copy for bool

impl Debug for bool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for bool

fn default() -> bool

Returns the default value of false

impl DisjointBitOr for bool

unsafe fn disjoint_bitor(self, other: Self) -> Self

🔬This is a nightly-only experimental API. (core_intrinsics_fallbacks)

See super::disjoint_bitor; we just need the trait indirection to handle different types since calling intrinsics with generics doesn’t work.

impl Display for bool

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Distribution<bool> for RangeFull

fn sample(&self, source: &mut (impl Rng + ?Sized)) -> bool

🔬This is a nightly-only experimental API. (random #130703)

Samples a random value from the distribution, using the specified random source.

impl Eq for bool

impl From<bool> for u8

fn from(b: bool) -> Self

Converts from bool to u8 , by turning false into 0 and true into 1.

Examples

assert_eq!(u8::from(false), 0);

assert_eq!(u8::from(true), 1);

impl From<bool> for u16

fn from(b: bool) -> Self

Converts from bool to u16 , by turning false into 0 and true into 1.

Examples

assert_eq!(u16::from(false), 0);

assert_eq!(u16::from(true), 1);

impl From<bool> for u32

fn from(b: bool) -> Self

Converts from bool to u32 , by turning false into 0 and true into 1.

Examples

assert_eq!(u32::from(false), 0);

assert_eq!(u32::from(true), 1);

impl From<bool> for u64

fn from(b: bool) -> Self

Converts from bool to u64 , by turning false into 0 and true into 1.

Examples

assert_eq!(u64::from(false), 0);

assert_eq!(u64::from(true), 1);

impl From<bool> for u128

fn from(b: bool) -> Self

Converts from bool to u128 , by turning false into 0 and true into 1.

Examples

assert_eq!(u128::from(false), 0);

assert_eq!(u128::from(true), 1);

impl From<bool> for usize

fn from(b: bool) -> Self

Converts from bool to usize , by turning false into 0 and true into 1.

Examples

assert_eq!(usize::from(false), 0);

assert_eq!(usize::from(true), 1);

impl From<bool> for i8

fn from(b: bool) -> Self

Converts from bool to i8 , by turning false into 0 and true into 1.

Examples

assert_eq!(i8::from(false), 0);

assert_eq!(i8::from(true), 1);

impl From<bool> for i16

fn from(b: bool) -> Self

Converts from bool to i16 , by turning false into 0 and true into 1.

Examples

assert_eq!(i16::from(false), 0);

assert_eq!(i16::from(true), 1);

impl From<bool> for i32

fn from(b: bool) -> Self

Converts from bool to i32 , by turning false into 0 and true into 1.

Examples

assert_eq!(i32::from(false), 0);

assert_eq!(i32::from(true), 1);

impl From<bool> for i64

fn from(b: bool) -> Self

Converts from bool to i64 , by turning false into 0 and true into 1.

Examples

assert_eq!(i64::from(false), 0);

assert_eq!(i64::from(true), 1);

impl From<bool> for i128

fn from(b: bool) -> Self

Converts from bool to i128 , by turning false into 0 and true into 1.

Examples

assert_eq!(i128::from(false), 0);

assert_eq!(i128::from(true), 1);

impl From<bool> for isize

fn from(b: bool) -> Self

Converts from bool to isize , by turning false into 0 and true into 1.

Examples

assert_eq!(isize::from(false), 0);

assert_eq!(isize::from(true), 1);

impl From<bool> for f16

fn from(small: bool) -> Self

Converts a bool to f16 losslessly. The resulting value is positive 0.0 for false and 1.0 for true values.

Examples

#![feature(f16)]

let x = f16::from(false);
assert_eq!(x, 0.0);
assert!(x.is_sign_positive());

let y = f16::from(true);
assert_eq!(y, 1.0);

impl From<bool> for f32

fn from(small: bool) -> Self

Converts a bool to f32 losslessly. The resulting value is positive 0.0 for false and 1.0 for true values.

Examples

let x = f32::from(false);
assert_eq!(x, 0.0);
assert!(x.is_sign_positive());

let y = f32::from(true);
assert_eq!(y, 1.0);

impl From<bool> for f64

fn from(small: bool) -> Self

Converts a bool to f64 losslessly. The resulting value is positive 0.0 for false and 1.0 for true values.

Examples

let x = f64::from(false);
assert_eq!(x, 0.0);
assert!(x.is_sign_positive());

let y = f64::from(true);
assert_eq!(y, 1.0);

impl From<bool> for f128

fn from(small: bool) -> Self

Converts a bool to f128 losslessly. The resulting value is positive 0.0 for false and 1.0 for true values.

Examples

#![feature(f128)]

let x = f128::from(false);
assert_eq!(x, 0.0);
assert!(x.is_sign_positive());

let y = f128::from(true);
assert_eq!(y, 1.0);

impl From<bool> for AtomicBool

fn from(b: bool) -> Self

Converts a bool into an AtomicBool.

Examples

use std::sync::atomic::AtomicBool;
let atomic_bool = AtomicBool::from(true);
assert_eq!(format!("{atomic_bool:?}"), "true")

impl FromStr for bool

fn from_str(s: &str) -> Result<bool, ParseBoolError>

Parse a bool from a string.

The only accepted values are "true" and "false". Any other input will return an error.

Examples

use std::str::FromStr;

assert_eq!(FromStr::from_str("true"), Ok(true));
assert_eq!(FromStr::from_str("false"), Ok(false));
assert!(<bool as FromStr>::from_str("not even a boolean").is_err());

Note, in many cases, the .parse() method on str is more proper.

assert_eq!("true".parse(), Ok(true));
assert_eq!("false".parse(), Ok(false));
assert!("not even a boolean".parse::<bool>().is_err());

type Err = ParseBoolError

The associated error which can be returned from parsing.

impl Hash for bool

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H: Hasher>(data: &[Self], state: &mut H)

where Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Not for bool

type Output = bool

The resulting type after applying the ! operator.

fn not(self) -> bool

Performs the unary ! operation.

impl Not for &bool

type Output = <bool as Not>::Output

The resulting type after applying the ! operator.

fn not(self) -> <bool as Not>::Output

Performs the unary ! operation.

impl Ord for bool

fn cmp(&self, other: &bool) -> Ordering

This method returns an Ordering between self and other.

fn min(self, other: bool) -> bool

Compares and returns the minimum of two values.

fn max(self, other: bool) -> bool

Compares and returns the maximum of two values.

fn clamp(self, min: bool, max: bool) -> bool

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to #147781)

Restrict a value to a certain range.

impl PartialEq for bool

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Self) -> bool

Inequality operator !=.

impl PartialOrd for bool

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

This method returns an ordering between self and other values if one exists.

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

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Self) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Self) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Self) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StructuralPartialEq for bool

impl TryFrom<i8> for bool

fn try_from(i: i8) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_i8), Ok(false));

assert_eq!(bool::try_from(1_i8), Ok(true));

assert!(bool::try_from(2_i8).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<i16> for bool

fn try_from(i: i16) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_i16), Ok(false));

assert_eq!(bool::try_from(1_i16), Ok(true));

assert!(bool::try_from(2_i16).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<i32> for bool

fn try_from(i: i32) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_i32), Ok(false));

assert_eq!(bool::try_from(1_i32), Ok(true));

assert!(bool::try_from(2_i32).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<i64> for bool

fn try_from(i: i64) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_i64), Ok(false));

assert_eq!(bool::try_from(1_i64), Ok(true));

assert!(bool::try_from(2_i64).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<i128> for bool

fn try_from(i: i128) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_i128), Ok(false));

assert_eq!(bool::try_from(1_i128), Ok(true));

assert!(bool::try_from(2_i128).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<u8> for bool

fn try_from(i: u8) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_u8), Ok(false));

assert_eq!(bool::try_from(1_u8), Ok(true));

assert!(bool::try_from(2_u8).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<u16> for bool

fn try_from(i: u16) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_u16), Ok(false));

assert_eq!(bool::try_from(1_u16), Ok(true));

assert!(bool::try_from(2_u16).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<u32> for bool

fn try_from(i: u32) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_u32), Ok(false));

assert_eq!(bool::try_from(1_u32), Ok(true));

assert!(bool::try_from(2_u32).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<u64> for bool

fn try_from(i: u64) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_u64), Ok(false));

assert_eq!(bool::try_from(1_u64), Ok(true));

assert!(bool::try_from(2_u64).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl TryFrom<u128> for bool

fn try_from(i: u128) -> Result<Self, Self::Error>

Tries to create a bool from an integer type. Returns an error if the integer is not 0 or 1.

Examples

assert_eq!(bool::try_from(0_u128), Ok(false));

assert_eq!(bool::try_from(1_u128), Ok(true));

assert!(bool::try_from(2_u128).is_err());

type Error = TryFromIntError

The type returned in the event of a conversion error.

impl UseCloned for bool