Primitive Type unit
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() {}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();
};Trait Implementations
impl Clone for ()fn clone(&self) -> Self
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from
source. Read more
impl Debug for ()fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
impl Default for ()fn default()Returns the default value of ()
impl Extend<()> for ()fn extend<T>(&mut self, iter: T)
where
T: IntoIterator<Item = ()>,
Extends a collection with the contents of an iterator. Read more
fn extend_one(&mut self, _item: ())🔬This is a nightly-only experimental API. (
extend_one #72631)
Extends a collection with exactly one element.
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
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());fn from_iter<I>(iter: I)
where
I: IntoIterator<Item = ()>,
Creates a value from an iterator. Read more
impl Hash for ()fn hash<H>(&self, _state: &mut H)
where
H: Hasher,fn hash_slice<H>(data: &[Self], state: &mut H)
where
H: Hasher,
Self: Sized,impl Ord for ()fn cmp(&self, _other: &()) -> Orderingfn max(self, other: Self) -> Self
where
Self: Sized,
Compares and returns the maximum of two values. Read more
fn min(self, other: Self) -> Self
where
Self: Sized,
Compares and returns the minimum of two values. Read more
fn clamp(self, min: Self, max: Self) -> Self
where
Self: Sized + PartialOrd,
Restrict a value to a certain interval. Read more
impl PartialEq for ()fn eq(&self, _other: &()) -> bool
This method tests for
self and other values to be equal, and is used by ==.
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.
impl PartialOrd for ()fn partial_cmp(&self, _: &()) -> Option<Ordering>fn lt(&self, other: &Rhs) -> boolfn 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
fn gt(&self, other: &Rhs) -> boolfn 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
impl Termination for ()fn report(self) -> ExitCode
Is called to get the representation of the value as status code. This status code is returned to the operating system.
impl ConstParamTy for ()impl Copy for ()impl Eq for ()impl StructuralEq for ()impl StructuralPartialEq for ()Auto Trait Implementations
impl RefUnwindSafe for ()impl Send for ()impl Sync for ()impl Unpin for ()impl UnwindSafe for ()Blanket Implementations
impl<T> Any for T
where
T: 'static + ?Sized,impl<T> Borrow<T> for T
where
T: ?Sized,impl<T> BorrowMut<T> for T
where
T: ?Sized,impl<T> From<T> for Tfn from(t: T) -> TReturns the argument unchanged.
impl<T, U> Into<U> for T
where
U: From<T>,fn into(self) -> UCalls U::from(self).
That is, this conversion is whatever the implementation of From<T> for U chooses to do.
impl<T> ToOwned for T
where
T: Clone,type Owned = T
The resulting type after obtaining ownership.
fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
fn clone_into(&self, target: &mut T)
Uses borrowed data to replace owned data, usually by cloning. Read more
impl<T, U> TryFrom<U> for T
where
U: Into<T>,type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
impl<T, U> TryInto<U> for T
where
U: TryFrom<T>,type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/primitive.unit.html