Primitive Type unit

1.0.0 ·
Expand description

The () type, also called “unit”.

The () type has exactly one value (), and is used when there is no other meaningful value that could be returned. () is most commonly seen implicitly: functions without a -> ... implicitly have return type (), that is, these are equivalent:

fn long() -> () {}

fn short() {}
Run

The semicolon ; can be used to discard the result of an expression at the end of a block, making the expression (and thus the block) evaluate to (). For example,

fn returns_i64() -> i64 {
    1i64
}
fn returns_unit() {
    1i64;
}

let is_i64 = {
    returns_i64()
};
let is_unit = {
    returns_i64();
};
Run

Implementations§

Trait Implementations§

source§

impl Clone for ()

source§

fn clone(&self) -> Self

Returns a copy of the value. Read more
source§

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

Performs copy-assignment from source. Read more
source§

impl Debug for ()

source§

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

Formats the value using the given formatter. Read more
source§

impl Default for ()

source§

fn default()

Returns the default value of ()

source§

impl Eq for ()

1.28.0 · source§

impl Extend<()> for ()

source§

fn extend<T: IntoIterator<Item = ()>>(&mut self, iter: T)

Extends a collection with the contents of an iterator. Read more
source§

fn extend_one(&mut self, _item: ())

🔬This is a nightly-only experimental API. (extend_one #72631)
Extends a collection with exactly one element.
source§

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one #72631)
Reserves capacity in a collection for the given number of additional elements. Read more
1.23.0 · source§

impl FromIterator<()> for ()

Collapses all unit items from an iterator into one.

This is more useful when combined with higher-level abstractions, like collecting to a Result<(), E> where you only care about errors:

use std::io::*;
let data = vec![1, 2, 3, 4, 5];
let res: Result<()> = data.iter()
    .map(|x| writeln!(stdout(), "{x}"))
    .collect();
assert!(res.is_ok());
Run
source§

fn from_iter<I: IntoIterator<Item = ()>>(iter: I) -> Self

Creates a value from an iterator. Read more
source§

impl Hash for ()

source§

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

Feeds this value into the given Hasher. Read more
1.3.0 · source§

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

Feeds a slice of this type into the given Hasher. Read more
source§

impl Ord for ()

source§

fn cmp(&self, _other: &()) -> Ordering

This method returns an Ordering between self and other. Read more
1.21.0 · source§

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

Compares and returns the maximum of two values. Read more
1.21.0 · source§

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

Compares and returns the minimum of two values. Read more
1.50.0 · source§

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
source§

impl PartialEq<()> for ()

source§

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

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

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

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl PartialOrd<()> for ()

source§

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

This method returns an ordering between self and other values if one exists. Read more
source§

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

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

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

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

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

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

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

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

impl ConstParamTy for ()

source§

impl Copy for ()

source§

impl StructuralEq for ()

source§

impl StructuralPartialEq for ()

Auto Trait Implementations§

§

impl Freeze for ()

§

impl RefUnwindSafe for ()

§

impl Send for ()

§

impl Sync for ()

§

impl Unpin for ()

§

impl UnwindSafe for ()

Blanket Implementations§

source§

impl<T> Any for Twhere T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for Twhere T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere T: ?Sized,

source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T, U> Into<U> for Twhere U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T> SizedTypeProperties for T

source§

const IS_ZST: bool = _

🔬This is a nightly-only experimental API. (sized_type_properties)
true if this type requires no storage. false if its size is greater than zero. Read more
source§

impl<T> SpecOptionPartialEq for Twhere T: PartialEq<T>,

source§

default fn eq(l: &Option<T>, r: &Option<T>) -> bool

🔬This is a nightly-only experimental API. (spec_option_partial_eq)
source§

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
source§

impl<T> Printable for Twhere T: Copy + Debug,