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Enum std::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);

Variants

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

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

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

Methods

impl Ordering [src]

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);

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);

🔬 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);

🔬 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);

Trait Implementations

impl PartialEq<Ordering> for Ordering [src]

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

This method tests for !=.

impl Clone for Ordering [src]

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl Eq for Ordering [src]

impl Debug for Ordering [src]

Formats the value using the given formatter.

impl Ord for Ordering [src]

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

impl Copy for Ordering [src]

impl Hash for Ordering [src]

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

Feeds a slice of this type into the state provided.

impl PartialOrd<Ordering> for Ordering [src]

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

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

© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/cmp/enum.Ordering.html