Enum std::cmp::Ordering

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

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);
Run

Variants§

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Less = -1

An ordering where a compared value is less than another.

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Equal = 0

An ordering where a compared value is equal to another.

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Greater = 1

An ordering where a compared value is greater than another.

Implementations§

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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);
Run
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);
Run
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);
Run
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);
Run
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);
Run
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);
Run
const: 1.48.0 · source

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);
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
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);
Run
1.17.0 · source

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);
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Trait Implementations§

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impl Clone for Ordering

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fn clone(&self) -> Ordering

Returns a copy of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Ordering

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl Hash for Ordering

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fn hash<__H>(&self, state: &mut __H)
where __H: Hasher,

Feeds this value into the given Hasher. Read more
1.3.0 · source§

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
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impl Ord for Ordering

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

This method returns an Ordering between self and other. Read more
1.21.0 · source§

fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
1.21.0 · source§

fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
1.50.0 · source§

fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl PartialEq for Ordering

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fn eq(&self, other: &Ordering) -> bool

This method tests for self and other values to be equal, and is used by ==.
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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.
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impl PartialOrd for Ordering

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

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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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
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fn gt(&self, other: &Rhs) -> bool

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

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impl Eq for Ordering

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impl StructuralPartialEq for Ordering

Auto Trait Implementations§

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

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

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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.