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>

🔬This is a nightly-only experimental API. (bool_to_result #142748)

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

#![feature(bool_to_result)]

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

#![feature(bool_to_result)]

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>

🔬This is a nightly-only experimental API. (bool_to_result #142748)

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

Examples

#![feature(bool_to_result)]

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

#![feature(bool_to_result)]

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);

Trait Implementations

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 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 for bool

type Output = bool

The resulting type after applying the & operator.

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

Performs the & operation.

impl BitAndAssign<&bool> for bool

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

Performs the &= operation.

impl BitAndAssign for bool

fn bitand_assign(&mut self, other: 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 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 for bool

type Output = bool

The resulting type after applying the | operator.

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

Performs the | operation.

impl BitOrAssign<&bool> for bool

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

Performs the |= operation.

impl BitOrAssign for bool

fn bitor_assign(&mut self, other: 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 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 for bool

type Output = bool

The resulting type after applying the ^ operator.

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

Performs the ^ operation.

impl BitXorAssign<&bool> for bool

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

Performs the ^= operation.

impl BitXorAssign for bool

fn bitxor_assign(&mut self, other: 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 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 Not for bool

type Output = bool

The resulting type after applying the ! operator.

fn not(self) -> bool

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.

impl PartialEq for bool

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

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 Copy for bool

impl Eq for bool