1.0.0[]Primitive Type unit

The () type, sometimes called "unit" or "nil".

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

Trait Implementations

impl PartialOrd<()> for ()
[src]

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

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

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

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

impl Ord for ()
[src]

Compares and returns the maximum of two values. Read more

Compares and returns the minimum of two values. Read more

impl Eq for ()
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impl PartialEq<()> for ()
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impl Hash for ()
[src]

Feeds a slice of this type into the given [Hasher]. Read more

impl FromIterator<()> for ()
1.23.0
[src]

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

impl Default for ()
[src]

Returns the default value of ()

impl Debug for ()
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impl Extend<()> for ()
1.28.0
[src]

impl Termination for ()
[src]