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>

🔬 This is a nightly-only experimental API. (bool_to_option #80967)

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

Examples

#![feature(bool_to_option)]

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

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

Trait Implementations

impl<'_> BitAnd<&'_ bool> for bool

type Output = <bool as BitAnd<bool>>::Output

The resulting type after applying the & operator.

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

Performs the & operation.

impl<'_, '_> BitAnd<&'_ bool> for &'_ bool

type Output = <bool as BitAnd<bool>>::Output

The resulting type after applying the & operator.

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

Performs the & operation.

impl BitAnd<bool> for bool

type Output = bool

The resulting type after applying the & operator.

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

Performs the & operation.

impl<'a> BitAnd<bool> for &'a bool

type Output = <bool as BitAnd<bool>>::Output

The resulting type after applying the & operator.

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

Performs the & operation.

impl<'_> BitAndAssign<&'_ bool> for bool

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

Performs the &= operation.

impl BitAndAssign<bool> for bool

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

Performs the &= operation.

impl<'_, '_> BitOr<&'_ bool> for &'_ bool

type Output = <bool as BitOr<bool>>::Output

The resulting type after applying the | operator.

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

Performs the | operation.

impl<'_> BitOr<&'_ bool> for bool

type Output = <bool as BitOr<bool>>::Output

The resulting type after applying the | operator.

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

Performs the | operation.

impl<'a> BitOr<bool> for &'a bool

type Output = <bool as BitOr<bool>>::Output

The resulting type after applying the | operator.

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

Performs the | operation.

impl BitOr<bool> for bool

type Output = bool

The resulting type after applying the | operator.

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

Performs the | operation.

impl<'_> BitOrAssign<&'_ bool> for bool

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

Performs the |= operation.

impl BitOrAssign<bool> for bool

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

Performs the |= operation.

impl<'_, '_> BitXor<&'_ bool> for &'_ bool

type Output = <bool as BitXor<bool>>::Output

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

impl<'_> BitXor<&'_ bool> for bool

type Output = <bool as BitXor<bool>>::Output

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

impl BitXor<bool> for bool

type Output = bool

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

impl<'a> BitXor<bool> for &'a bool

type Output = <bool as BitXor<bool>>::Output

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

impl<'_> BitXorAssign<&'_ bool> for bool

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

Performs the ^= operation.

impl BitXorAssign<bool> for bool

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

Performs the ^= operation.

impl Clone for bool

pub fn clone(&self) -> bool

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for bool

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

Formats the value using the given formatter.

impl Default for bool

pub fn default() -> bool

Returns the default value of false

impl Display for bool

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

Formats the value using the given formatter.

impl FromStr for bool

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

Parse a bool from a string.

Yields a Result<bool, ParseBoolError>, because s may or may not actually be parseable.

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

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

Feeds this value into the given Hasher.

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

Feeds a slice of this type into the given Hasher.

impl Not for bool

type Output = bool

The resulting type after applying the ! operator.

pub 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.

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

Performs the unary ! operation.

impl Ord for bool

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

This method returns an Ordering between self and other.

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

Compares and returns the maximum of two values.

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

Compares and returns the minimum of two values.

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

Restrict a value to a certain interval.

impl PartialEq<bool> for bool

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl PartialOrd<bool> for bool

pub 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: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

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

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

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

This method tests greater than (for self and other) and is used by the > operator.

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

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

impl Copy for bool

impl Eq for bool