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>(&mut self, iter: T) where
T: IntoIterator<Item = ()>,
fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = ()>,
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>(iter: I) where
I: IntoIterator<Item = ()>,
fn from_iter<I>(iter: I) where
I: IntoIterator<Item = ()>,
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
1.61.0 · sourceimpl Termination for ()
impl Termination for ()
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