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 always demands a bool value. assert!, being an important macro in testing, checks whether an expression returns true.

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);

Methods

impl bool

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

🔬 This is a nightly-only experimental API. (bool_to_option #64260)

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

Examples

#![feature(bool_to_option)]

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

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

🔬 This is a nightly-only experimental API. (bool_to_option #64260)

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

Examples

#![feature(bool_to_option)]

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

Trait Implementations

impl Eq for bool

impl PartialEq<bool> for bool

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

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

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

This method tests for !=.

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 Default for bool

fn default() -> bool

Returns the default value of false

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

type Err = ParseBoolError

The associated error which can be returned from parsing.

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());

impl Hash for bool

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 Ord for bool

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

🔬 This is a nightly-only experimental API. (clamp #44095)

Restrict a value to a certain interval.

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

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

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

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

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

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

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

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

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<bool>>::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<bool>>::Output

The resulting type after applying the | operator.

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

Performs the | operation.

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

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

The resulting type after applying the & operator.

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.

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.

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

Performs the & operation.

impl Display for bool

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

Formats the value using the given formatter.

impl BitOrAssign<bool> 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 Debug for bool

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

Formats the value using the given formatter.

impl Clone for bool

fn clone(&self) -> bool

Returns a copy of the value.

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

Performs copy-assignment from source.

impl PartialOrd<bool> for bool

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

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

#[must_use] fn lt(&self, other: &Rhs) -> bool

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

#[must_use] fn le(&self, other: &Rhs) -> bool

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

#[must_use] fn gt(&self, other: &Rhs) -> bool

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

#[must_use] 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 BitXorAssign<bool> 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 Copy for bool