# Primitive Type unit 1.0.0 [−]

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]

#### `fn partial_cmp(&self, &()) -> Option<Ordering>`
[src]

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

#### `fn lt(&self, other: &Rhs) -> bool`
[src]

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

#### `fn le(&self, other: &Rhs) -> bool`
[src]

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) -> bool`
[src]

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

#### `fn ge(&self, other: &Rhs) -> bool`
[src]

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

### `impl Ord for ()`
[src]

#### `fn cmp(&self, _other: &()) -> Ordering`
[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `fn max(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self`
1.21.0
[src]

Compares and returns the minimum of two values. Read more

### `impl Debug for ()`
[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result<(), Error>`
[src]

Formats the value using the given formatter. Read more

### `impl Eq for ()`
[src]

### `impl PartialEq<()> for ()`
[src]

#### `fn eq(&self, _other: &()) -> bool`
[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `fn ne(&self, _other: &()) -> bool`
[src]

This method tests for `!=`.

### `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

#### `fn from_iter<I>(iter: I) where
I: IntoIterator<Item = ()>,`
[src]

Creates a value from an iterator. Read more

### `impl Hash for ()`
[src]

#### `fn hash<H>(&self, _state: &mut H) where
H: Hasher,`
[src]

Feeds this value into the given [`Hasher`]. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,`
1.3.0
[src]

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

### `impl Default for ()`
[src]

#### `fn default()`
[src]

Returns the default value of `()`

### `impl Termination for ()`
[src]

#### `fn report(self) -> i32`
[src]

🔬 This is a nightly-only experimental API. (`termination_trait` #43301)

Is called to get the representation of the value as status code. This status code is returned to the operating system. Read more

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
↑
  Move up in search results
↓
  Move down in search results
↹
  Switch tab
⏎
  Go to active search result
+ / -
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)