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

# Trait core::cmp::Ord 1.0.0 [−] [src]

    pub trait Ord: Eq + PartialOrd<Self> {
        fn cmp(&self, other: &Self) -> Ordering;

        fn max(self, other: Self) -> Self
        where
            Self: Sized,
        { ... }
        fn min(self, other: Self) -> Self
        where
            Self: Sized,
        { ... }
    }

Trait for types that form a total order.

An order is a total order if it is (for all `a`, `b` and `c`):

- total and antisymmetric: exactly one of `a < b`, `a == b` or `a > b` is true; and
- transitive, `a < b` and `b < c` implies `a < c`. The same must hold for both `==` and `>`.

## Derivable

This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a lexicographic ordering based on the top-to-bottom declaration order of the struct's members. When `derive`d on enums, variants are ordered by their top-to-bottom declaration order.

## How can I implement `Ord`?

`Ord` requires that the type also be `PartialOrd` and `Eq` (which requires `PartialEq`).

Then you must define an implementation for `cmp()`. You may find it useful to use `cmp()` on your type's fields.

Implementations of `PartialEq`, `PartialOrd`, and `Ord` must agree with each other. It's easy to accidentally make them disagree by deriving some of the traits and manually implementing others.

Here's an example where you want to sort people by height only, disregarding `id` and `name`:

    use std::cmp::Ordering;

    #[derive(Eq)]
    struct Person {
        id: u32,
        name: String,
        height: u32,
    }

    impl Ord for Person {
        fn cmp(&self, other: &Person) -> Ordering {
            self.height.cmp(&other.height)
        }
    }

    impl PartialOrd for Person {
        fn partial_cmp(&self, other: &Person) -> Option<Ordering> {
            Some(self.cmp(other))
        }
    }

    impl PartialEq for Person {
        fn eq(&self, other: &Person) -> bool {
            self.height == other.height
        }
    }Run

## Required Methods

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

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

By convention, `self.cmp(&other)` returns the ordering matching the expression `self <operator> other` if true.

# Examples

    use std::cmp::Ordering;

    assert_eq!(5.cmp(&10), Ordering::Less);
    assert_eq!(10.cmp(&5), Ordering::Greater);
    assert_eq!(5.cmp(&5), Ordering::Equal);Run

## Provided Methods

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

Compares and returns the maximum of two values.

Returns the second argument if the comparison determines them to be equal.

# Examples

    assert_eq!(2, 1.max(2));
    assert_eq!(2, 2.max(2));Run

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

Compares and returns the minimum of two values.

Returns the first argument if the comparison determines them to be equal.

# Examples

    assert_eq!(1, 1.min(2));
    assert_eq!(2, 2.min(2));Run

## Implementors

- `impl<T: Ord> Ord for Wrapping<T>`
- `impl<T: Ord + Zeroable> Ord for NonZero<T>`
- `impl<Ret> Ord for fn() -> Ret`
- `impl<Ret> Ord for extern "C" fn() -> Ret`
- `impl<Ret> Ord for unsafe fn() -> Ret`
- `impl<Ret> Ord for unsafe extern "C" fn() -> Ret`
- `impl<Ret, A> Ord for fn(_: A) -> Ret`
- `impl<Ret, A> Ord for extern "C" fn(_: A) -> Ret`
- `impl<Ret, A> Ord for extern "C" fn(_: A, ...) -> Ret`
- `impl<Ret, A> Ord for unsafe fn(_: A) -> Ret`
- `impl<Ret, A> Ord for unsafe extern "C" fn(_: A) -> Ret`
- `impl<Ret, A> Ord for unsafe extern "C" fn(_: A, ...) -> Ret`
- `impl<Ret, A, B> Ord for fn(_: A, _: B) -> Ret`
- `impl<Ret, A, B> Ord for extern "C" fn(_: A, _: B) -> Ret`
- `impl<Ret, A, B> Ord for extern "C" fn(_: A, _: B, ...) -> Ret`
- `impl<Ret, A, B> Ord for unsafe fn(_: A, _: B) -> Ret`
- `impl<Ret, A, B> Ord for unsafe extern "C" fn(_: A, _: B) -> Ret`
- `impl<Ret, A, B> Ord for unsafe extern "C" fn(_: A, _: B, ...) -> Ret`
- `impl<Ret, A, B, C> Ord for fn(_: A, _: B, _: C) -> Ret`
- `impl<Ret, A, B, C> Ord for extern "C" fn(_: A, _: B, _: C) -> Ret`
- `impl<Ret, A, B, C> Ord for extern "C" fn(_: A, _: B, _: C, ...) -> Ret`
- `impl<Ret, A, B, C> Ord for unsafe fn(_: A, _: B, _: C) -> Ret`
- `impl<Ret, A, B, C> Ord for unsafe extern "C" fn(_: A, _: B, _: C) -> Ret`
- `impl<Ret, A, B, C> Ord for unsafe extern "C" fn(_: A, _: B, _: C, ...) -> Ret`
- `impl<Ret, A, B, C, D> Ord for fn(_: A, _: B, _: C, _: D) -> Ret`
- `impl<Ret, A, B, C, D> Ord for extern "C" fn(_: A, _: B, _: C, _: D) -> Ret`
- `impl<Ret, A, B, C, D> Ord for extern "C" fn(_: A, _: B, _: C, _: D, ...) -> Ret`
- `impl<Ret, A, B, C, D> Ord for unsafe fn(_: A, _: B, _: C, _: D) -> Ret`
- `impl<Ret, A, B, C, D> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D) -> Ret`
- `impl<Ret, A, B, C, D> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, ...) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for fn(_: A, _: B, _: C, _: D, _: E) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, ...) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E) -> Ret`
- `impl<Ret, A, B, C, D, E> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F) -> Ret`
- `impl<Ret, A, B, C, D, E, F> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L, ...) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L) -> Ret`
- `impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Ord for unsafe extern "C" fn(_: A, _: B, _: C, _: D, _: E, _: F, _: G, _: H, _: I, _: J, _: K, _: L, ...) -> Ret`
- `impl<T: ?Sized> Ord for *const T`
- `impl<T: ?Sized> Ord for *mut T`
- `impl<T: ?Sized> Ord for PhantomData<T>`
- `impl Ord for ()`
- `impl Ord for bool`
- `impl Ord for char`
- `impl Ord for usize`
- `impl Ord for u8`
- `impl Ord for u16`
- `impl Ord for u32`
- `impl Ord for u64`
- `impl Ord for u128`
- `impl Ord for isize`
- `impl Ord for i8`
- `impl Ord for i16`
- `impl Ord for i32`
- `impl Ord for i64`
- `impl Ord for i128`
- `impl Ord for !`
- `impl<'a, A: ?Sized> Ord for &'a A where
  A: Ord,`
- `impl<'a, A: ?Sized> Ord for &'a mut A where
  A: Ord,`
- `impl<T: Ord> Ord for Reverse<T>`
- `impl Ord for Ordering`
- `impl Ord for TypeId`
- `impl<T: Ord> Ord for [T; 0]`
- `impl<T: Ord> Ord for [T; 1]`
- `impl<T: Ord> Ord for [T; 2]`
- `impl<T: Ord> Ord for [T; 3]`
- `impl<T: Ord> Ord for [T; 4]`
- `impl<T: Ord> Ord for [T; 5]`
- `impl<T: Ord> Ord for [T; 6]`
- `impl<T: Ord> Ord for [T; 7]`
- `impl<T: Ord> Ord for [T; 8]`
- `impl<T: Ord> Ord for [T; 9]`
- `impl<T: Ord> Ord for [T; 10]`
- `impl<T: Ord> Ord for [T; 11]`
- `impl<T: Ord> Ord for [T; 12]`
- `impl<T: Ord> Ord for [T; 13]`
- `impl<T: Ord> Ord for [T; 14]`
- `impl<T: Ord> Ord for [T; 15]`
- `impl<T: Ord> Ord for [T; 16]`
- `impl<T: Ord> Ord for [T; 17]`
- `impl<T: Ord> Ord for [T; 18]`
- `impl<T: Ord> Ord for [T; 19]`
- `impl<T: Ord> Ord for [T; 20]`
- `impl<T: Ord> Ord for [T; 21]`
- `impl<T: Ord> Ord for [T; 22]`
- `impl<T: Ord> Ord for [T; 23]`
- `impl<T: Ord> Ord for [T; 24]`
- `impl<T: Ord> Ord for [T; 25]`
- `impl<T: Ord> Ord for [T; 26]`
- `impl<T: Ord> Ord for [T; 27]`
- `impl<T: Ord> Ord for [T; 28]`
- `impl<T: Ord> Ord for [T; 29]`
- `impl<T: Ord> Ord for [T; 30]`
- `impl<T: Ord> Ord for [T; 31]`
- `impl<T: Ord> Ord for [T; 32]`
- `impl<T: Ord + Copy> Ord for Cell<T>`
- `impl<T: ?Sized + Ord> Ord for RefCell<T>`
- `impl<T: Ord> Ord for Option<T>`
- `impl<T: Ord, E: Ord> Ord for Result<T, E>`
- `impl<T: Ord> Ord for [T]`
- `impl Ord for str`
- `impl Ord for Error`
- `impl<A: Ord + ?Sized> Ord for (A,) where
  A: ,`
- `impl<A: Ord, B: Ord + ?Sized> Ord for (A, B) where
  B: ,`
- `impl<A: Ord, B: Ord, C: Ord + ?Sized> Ord for (A, B, C) where
  C: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord + ?Sized> Ord for (A, B, C, D) where
  D: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord + ?Sized> Ord for (A, B, C, D, E) where
  E: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord + ?Sized> Ord for (A, B, C, D, E, F) where
  F: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord + ?Sized> Ord for (A, B, C, D, E, F, G) where
  G: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord, H: Ord + ?Sized> Ord for (A, B, C, D, E, F, G, H) where
  H: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord, H: Ord, I: Ord + ?Sized> Ord for (A, B, C, D, E, F, G, H, I) where
  I: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord, H: Ord, I: Ord, J: Ord + ?Sized> Ord for (A, B, C, D, E, F, G, H, I, J) where
  J: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord, H: Ord, I: Ord, J: Ord, K: Ord + ?Sized> Ord for (A, B, C, D, E, F, G, H, I, J, K) where
  K: ,`
- `impl<A: Ord, B: Ord, C: Ord, D: Ord, E: Ord, F: Ord, G: Ord, H: Ord, I: Ord, J: Ord, K: Ord, L: Ord + ?Sized> Ord for (A, B, C, D, E, F, G, H, I, J, K, L) where
  L: ,`

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