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

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

    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.

## Implementations

### `impl Ordering`[src]

#### `#[must_use]pub const fn reverse(self) -> Ordering`[src]

Reverses 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 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

#### `#[must_use]pub const fn then(self, other: Ordering) -> Ordering`1.17.0[src]

Chains two orderings.

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

# Examples

    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

#### `#[must_use]pub fn then_with<F: FnOnce() -> Ordering>(self, f: F) -> Ordering`1.17.0[src]

Chains the ordering with the given function.

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

# Examples

    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`[src]

Returns a copy of the value. Read more

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

Performs copy-assignment from `source`. Read more

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

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

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

Formats the value using the given formatter. Read more

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

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

#### `fn hash<__H: Hasher>(&self, state: &mut __H)`[src]

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

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

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

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

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

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

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

Compares and returns the maximum of two values. Read more

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

Compares and returns the minimum of two values. Read more

#### `#[must_use]fn clamp(self, min: Self, max: Self) -> Self where
Self: Sized,` [src]

🔬 This is a nightly-only experimental API. (`clamp` #44095)

Restrict a value to a certain interval. Read more

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

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

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

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

This method tests for `!=`.

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

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

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

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

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

#### `#[must_use]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

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

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

#### `#[must_use]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 StructuralPartialEq for Ordering`[src]

## Auto Trait Implementations

### `impl Send for Ordering`

### `impl Sync for Ordering`

### `impl Unpin for Ordering`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&Self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `fn borrow(&Self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut Self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T`[src]

#### `fn from(T) -> T`[src]

Performs the conversion.

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `fn into(Self) -> U`[src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `fn try_from(U) -> Result<T, <T as TryFrom<U>>::Error>`[src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

#### `type Error = <U as TryFrom<T>>::Error`

The type returned in the event of a conversion error.

#### `fn try_into(Self) -> Result<U, <U as TryFrom<T>>::Error>`[src]

Performs the conversion.