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() {}
RunThe 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();
};
RunTrait Implementations
1.28.0 · sourceimpl Extend<()> for ()
impl Extend<()> for ()
sourcefn extend<T: IntoIterator<Item = ()>>(&mut self, iter: T)
fn extend<T: IntoIterator<Item = ()>>(&mut self, iter: T)
Extends a collection with the contents of an iterator. Read more
sourcefn extend_reserve(&mut self, additional: usize)
fn extend_reserve(&mut self, additional: usize)
Reserves capacity in a collection for the given number of additional elements. Read more
1.23.0 · sourceimpl FromIterator<()> for ()
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());
Runsourcefn from_iter<I: IntoIterator<Item = ()>>(iter: I) -> Self
fn from_iter<I: IntoIterator<Item = ()>>(iter: I) -> Self
Creates a value from an iterator. Read more
sourceimpl Ord for ()
impl Ord for ()
sourceimpl PartialOrd<()> for ()
impl PartialOrd<()> for ()
sourcefn partial_cmp(&self, _: &()) -> Option<Ordering>
fn partial_cmp(&self, _: &()) -> Option<Ordering>
This method returns an ordering between self
and other
values if one exists. Read more
sourcefn lt(&self, other: &Rhs) -> bool
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self
and other
) and is used by the <
operator. Read more
sourcefn le(&self, other: &Rhs) -> bool
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
impl Copy for ()
impl Eq for ()
Auto Trait Implementations
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more