Primitive Type bool
1.0.0 ·Expand description
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);
Run§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!"),
}
RunAlso, 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);
RunImplementations§
source§impl bool
impl bool
1.62.0 · sourcepub fn then_some<T>(self, t: T) -> Option<T>
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));
Runlet 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);
Run1.50.0 · sourcepub fn then<T, F: FnOnce() -> T>(self, f: F) -> Option<T>
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));
Runlet 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);
RunTrait Implementations§
1.22.0 · source§impl BitAndAssign<&bool> for bool
impl BitAndAssign<&bool> for bool
source§fn bitand_assign(&mut self, other: &bool)
fn bitand_assign(&mut self, other: &bool)
&=
operation. Read moresource§impl<T, const N: usize> BitAndAssign<bool> for Mask<T, N>
impl<T, const N: usize> BitAndAssign<bool> for Mask<T, N>
source§fn bitand_assign(&mut self, rhs: bool)
fn bitand_assign(&mut self, rhs: bool)
&=
operation. Read more1.8.0 · source§impl BitAndAssign for bool
impl BitAndAssign for bool
source§fn bitand_assign(&mut self, other: bool)
fn bitand_assign(&mut self, other: bool)
&=
operation. Read more1.22.0 · source§impl BitOrAssign<&bool> for bool
impl BitOrAssign<&bool> for bool
source§fn bitor_assign(&mut self, other: &bool)
fn bitor_assign(&mut self, other: &bool)
|=
operation. Read moresource§impl<T, const N: usize> BitOrAssign<bool> for Mask<T, N>
impl<T, const N: usize> BitOrAssign<bool> for Mask<T, N>
source§fn bitor_assign(&mut self, rhs: bool)
fn bitor_assign(&mut self, rhs: bool)
|=
operation. Read more1.8.0 · source§impl BitOrAssign for bool
impl BitOrAssign for bool
source§fn bitor_assign(&mut self, other: bool)
fn bitor_assign(&mut self, other: bool)
|=
operation. Read more1.22.0 · source§impl BitXorAssign<&bool> for bool
impl BitXorAssign<&bool> for bool
source§fn bitxor_assign(&mut self, other: &bool)
fn bitxor_assign(&mut self, other: &bool)
^=
operation. Read moresource§impl<T, const N: usize> BitXorAssign<bool> for Mask<T, N>
impl<T, const N: usize> BitXorAssign<bool> for Mask<T, N>
source§fn bitxor_assign(&mut self, rhs: bool)
fn bitxor_assign(&mut self, rhs: bool)
^=
operation. Read more1.8.0 · source§impl BitXorAssign for bool
impl BitXorAssign for bool
source§fn bitxor_assign(&mut self, other: bool)
fn bitxor_assign(&mut self, other: bool)
^=
operation. Read more1.24.0 · source§impl From<bool> for AtomicBool
impl From<bool> for AtomicBool
source§impl FromStr for bool
impl FromStr for bool
source§fn from_str(s: &str) -> Result<bool, ParseBoolError>
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());
RunNote, 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());
Run