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Enum std::cmp::Ordering

#[repr(i8)]pub enum Ordering {
    Less = -1,
    Equal = 0,
    Greater = 1,
}

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

Examples

use std::cmp::Ordering;

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

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

assert_eq!(2.cmp(&1), Ordering::Greater);

Variants

Less = -1

An ordering where a compared value is less than another.

Equal = 0

An ordering where a compared value is equal to another.

Greater = 1

An ordering where a compared value is greater than another.

Implementations

source 
impl Ordering
1.53.0 (const: 1.53.0)source 
pub const fn is_eq(self) -> bool

Returns true if the ordering is the Equal variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_eq(), false);
assert_eq!(Ordering::Equal.is_eq(), true);
assert_eq!(Ordering::Greater.is_eq(), false);
1.53.0 (const: 1.53.0)source 
pub const fn is_ne(self) -> bool

Returns true if the ordering is not the Equal variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_ne(), true);
assert_eq!(Ordering::Equal.is_ne(), false);
assert_eq!(Ordering::Greater.is_ne(), true);
1.53.0 (const: 1.53.0)source 
pub const fn is_lt(self) -> bool

Returns true if the ordering is the Less variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_lt(), true);
assert_eq!(Ordering::Equal.is_lt(), false);
assert_eq!(Ordering::Greater.is_lt(), false);
1.53.0 (const: 1.53.0)source 
pub const fn is_gt(self) -> bool

Returns true if the ordering is the Greater variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_gt(), false);
assert_eq!(Ordering::Equal.is_gt(), false);
assert_eq!(Ordering::Greater.is_gt(), true);
1.53.0 (const: 1.53.0)source 
pub const fn is_le(self) -> bool

Returns true if the ordering is either the Less or Equal variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_le(), true);
assert_eq!(Ordering::Equal.is_le(), true);
assert_eq!(Ordering::Greater.is_le(), false);
1.53.0 (const: 1.53.0)source 
pub const fn is_ge(self) -> bool

Returns true if the ordering is either the Greater or Equal variant.

Examples
use std::cmp::Ordering;

assert_eq!(Ordering::Less.is_ge(), false);
assert_eq!(Ordering::Equal.is_ge(), true);
assert_eq!(Ordering::Greater.is_ge(), true);
const: 1.48.0source 
pub const fn reverse(self) -> Ordering

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);

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);
1.17.0 (const: 1.48.0)source 
pub const fn then(self, other: Ordering) -> Ordering

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);
1.17.0source 
pub fn then_with<F>(self, f: F) -> Ordering
where
    F: FnOnce() -> Ordering,

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);

Trait Implementations

source 
impl Clone for Ordering
source 
fn clone(&self) -> Ordering
Returns a copy of the value. Read more
source 
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source. Read more
source 
impl Debug for Ordering
source 
fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>
Formats the value using the given formatter. Read more
source 
impl Hash for Ordering
source 
fn hash<__H>(&self, state: &mut __H)
where
    __H: Hasher,
Feeds this value into the given Hasher. Read more
1.3.0source 
fn hash_slice<H>(data: &[Self], state: &mut H)
where
    H: Hasher,
    Self: Sized,
Feeds a slice of this type into the given Hasher. Read more
source 
impl Ord for Ordering
source 
fn cmp(&self, other: &Ordering) -> Ordering
This method returns an Ordering between self and other. Read more
1.21.0source 
fn max(self, other: Self) -> Self
where
    Self: Sized,
Compares and returns the maximum of two values. Read more
1.21.0source 
fn min(self, other: Self) -> Self
where
    Self: Sized,
Compares and returns the minimum of two values. Read more
1.50.0source 
fn clamp(self, min: Self, max: Self) -> Self
where
    Self: Sized + PartialOrd,
Restrict a value to a certain interval. Read more
source 
impl PartialEq for Ordering
source 
fn eq(&self, other: &Ordering) -> bool
This method tests for self and other values to be equal, and is used by ==.
source 
fn ne(&self, other: &Rhs) -> bool
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source 
impl PartialOrd for Ordering
source 
fn partial_cmp(&self, other: &Ordering) -> Option<Ordering>
This method returns an ordering between self and other values if one exists. Read more
source 
fn lt(&self, other: &Rhs) -> bool
This method tests less than (for self and other) and is used by the < operator. Read more
source 
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
source 
fn gt(&self, other: &Rhs) -> bool
This method tests greater than (for self and other) and is used by the > operator. Read more
source 
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
source 
impl Copy for Ordering
source 
impl Eq for Ordering
source 
impl StructuralEq for Ordering
source 
impl StructuralPartialEq for Ordering

Auto Trait Implementations

impl RefUnwindSafe for Ordering
impl Send for Ordering
impl Sync for Ordering
impl Unpin for Ordering
impl UnwindSafe for Ordering

Blanket Implementations

source 
impl<T> Any for T
where
    T: 'static + ?Sized,
source 
fn type_id(&self) -> TypeId
Gets the TypeId of self. Read more
source 
impl<T> Borrow<T> for T
where
    T: ?Sized,
source 
fn borrow(&self) -> &T
Immutably borrows from an owned value. Read more
source 
impl<T> BorrowMut<T> for T
where
    T: ?Sized,
source 
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
source 
impl<T> From<T> for T
source 
fn from(t: T) -> T

Returns the argument unchanged.

source 
impl<T, U> Into<U> for T
where
    U: From<T>,
source 
fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source 
impl<T> ToOwned for T
where
    T: Clone,
 
type Owned = T
The resulting type after obtaining ownership.
source 
fn to_owned(&self) -> T
Creates owned data from borrowed data, usually by cloning. Read more
source 
fn clone_into(&self, target: &mut T)
Uses borrowed data to replace owned data, usually by cloning. Read more
source 
impl<T, U> TryFrom<U> for T
where
    U: Into<T>,
 
type Error = Infallible
The type returned in the event of a conversion error.
source 
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
Performs the conversion.
source 
impl<T, U> TryInto<U> for T
where
    U: TryFrom<T>,
 
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
source 
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
Performs the conversion.

© 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