core::cmp::Ordering - Rust
Description: API documentation for the Rust `Ordering` enum in crate `core`.
Keywords: rust, rustlang, rust-lang, Ordering

# Enum core::cmp::Ordering 1.0.0 [−] [src]

    pub enum Ordering {
        Less,
        Equal,
        Greater,
    }

An `Ordering` is the result of a comparison between two values.

# Examples

    use std::cmp::Ordering;

    let result = 1.cmp(&2);
    assert_eq!(Ordering::Less, result);

    let result = 1.cmp(&1);
    assert_eq!(Ordering::Equal, result);

    let result = 2.cmp(&1);
    assert_eq!(Ordering::Greater, result);Run

## Variants

`Less`

An ordering where a compared value is less [than another].

`Equal`

An ordering where a compared value is equal [to another].

`Greater`

An ordering where a compared value is greater [than another].

## Methods

### `impl Ordering`
[src]

#### `fn reverse(self) -> Ordering`

Reverse the `Ordering`.

- `Less` becomes `Greater`.
- `Greater` becomes `Less`.
- `Equal` becomes `Equal`.

# Examples

Basic behavior:

    use std::cmp::Ordering;

    assert_eq!(Ordering::Less.reverse(), Ordering::Greater);
    assert_eq!(Ordering::Equal.reverse(), Ordering::Equal);
    assert_eq!(Ordering::Greater.reverse(), Ordering::Less);Run

This method can be used to reverse a comparison:

    let mut data: &mut [_] = &mut [2, 10, 5, 8];

    // sort the array from largest to smallest.
    data.sort_by(|a, b| a.cmp(b).reverse());

    let b: &mut [_] = &mut [10, 8, 5, 2];
    assert!(data == b);Run

#### `fn then(self, other: Ordering) -> Ordering`

🔬 This is a nightly-only experimental API. (`ordering_chaining` #37053)

Chains two orderings.

Returns `self` when it's not `Equal`. Otherwise returns `other`.

# Examples

    #![feature(ordering_chaining)]

    use std::cmp::Ordering;

    let result = Ordering::Equal.then(Ordering::Less);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Less.then(Ordering::Equal);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Less.then(Ordering::Greater);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Equal.then(Ordering::Equal);
    assert_eq!(result, Ordering::Equal);

    let x: (i64, i64, i64) = (1, 2, 7);
    let y: (i64, i64, i64) = (1, 5, 3);
    let result = x.0.cmp(&y.0).then(x.1.cmp(&y.1)).then(x.2.cmp(&y.2));

    assert_eq!(result, Ordering::Less);Run

#### `fn then_with<F: FnOnce() -> Ordering>(self, f: F) -> Ordering`

🔬 This is a nightly-only experimental API. (`ordering_chaining` #37053)

Chains the ordering with the given function.

Returns `self` when it's not `Equal`. Otherwise calls `f` and returns the result.

# Examples

    #![feature(ordering_chaining)]

    use std::cmp::Ordering;

    let result = Ordering::Equal.then_with(|| Ordering::Less);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Less.then_with(|| Ordering::Equal);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Less.then_with(|| Ordering::Greater);
    assert_eq!(result, Ordering::Less);

    let result = Ordering::Equal.then_with(|| Ordering::Equal);
    assert_eq!(result, Ordering::Equal);

    let x: (i64, i64, i64) = (1, 2, 7);
    let y: (i64, i64, i64)  = (1, 5, 3);
    let result = x.0.cmp(&y.0).then_with(|| x.1.cmp(&y.1)).then_with(|| x.2.cmp(&y.2));

    assert_eq!(result, Ordering::Less);Run

## Trait Implementations

### `impl Clone for Ordering`
[src]

#### `fn clone(&self) -> Ordering`

Returns a copy of the value. Read more

#### `fn clone_from(&mut self, source: &Self)`

Performs copy-assignment from `source`. Read more

### `impl Copy for Ordering`
[src]

### `impl PartialEq for Ordering`
[src]

#### `fn eq(&self, __arg_0: &Ordering) -> bool`

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

#### `fn ne(&self, other: &Rhs) -> bool`

This method tests for `!=`.

### `impl Debug for Ordering`
[src]

#### `fn fmt(&self, __arg_0: &mut Formatter) -> Result`

Formats the value using the given formatter.

### `impl Hash for Ordering`
[src]

#### `fn hash<__H: Hasher>(&self, __arg_0: &mut __H)`

Feeds this value into the state given, updating the hasher as necessary.

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

Feeds a slice of this type into the state provided.

### `impl Eq for Ordering`
[src]

### `impl Ord for Ordering`
[src]

#### `fn cmp(&self, other: &Ordering) -> Ordering`

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

### `impl PartialOrd for Ordering`
[src]

#### `fn partial_cmp(&self, other: &Ordering) -> Option<Ordering>`

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

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

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

#### `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

#### `fn gt(&self, other: &Rhs) -> bool`

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

#### `fn 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

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