pub trait Ord: Eq + PartialOrd<Self> {
fn cmp(&self, other: &Self) -> Ordering;
fn max(self, other: Self) -> Self { ... }
fn min(self, other: Self) -> Self { ... }
fn clamp(self, min: Self, max: Self) -> Self { ... }
}
Expand description
Trait for types that form a total order.
Implementations must be consistent with the PartialOrd
implementation, and ensure
max
, min
, and clamp
are consistent with cmp
:
partial_cmp(a, b) == Some(cmp(a, b))
.max(a, b) == max_by(a, b, cmp)
(ensured by the default implementation).min(a, b) == min_by(a, b, cmp)
(ensured by the default implementation).- For
a.clamp(min, max)
, see the method docs (ensured by the default implementation).
It’s easy to accidentally make cmp
and partial_cmp
disagree by
deriving some of the traits and manually implementing others.
Corollaries
From the above and the requirements of PartialOrd
, it follows that <
defines a strict total order.
This means that for all a
, b
and c
:
- exactly one of
a < b
,a == b
ora > b
is true; and <
is transitive:a < b
andb < c
impliesa < 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 discriminants.
By default, the discriminant is smallest for variants at the top, and
largest for variants at the bottom. Here’s an example:
#[derive(PartialEq, Eq, PartialOrd, Ord)]
enum E {
Top,
Bottom,
}
assert!(E::Top < E::Bottom);
However, manually setting the discriminants can override this default behavior:
#[derive(PartialEq, Eq, PartialOrd, Ord)]
enum E {
Top = 2,
Bottom = 1,
}
assert!(E::Bottom < E::Top);
Lexicographical comparison
Lexicographical comparison is an operation with the following properties:
- Two sequences are compared element by element.
- The first mismatching element defines which sequence is lexicographically less or greater than the other.
- If one sequence is a prefix of another, the shorter sequence is lexicographically less than the other.
- If two sequence have equivalent elements and are of the same length, then the sequences are lexicographically equal.
- An empty sequence is lexicographically less than any non-empty sequence.
- Two empty sequences are lexicographically equal.
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.
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: &Self) -> Ordering {
self.height.cmp(&other.height)
}
}
impl PartialOrd for Person {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl PartialEq for Person {
fn eq(&self, other: &Self) -> bool {
self.height == other.height
}
}
Required methods
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);
Provided methods
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));
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));
Implementations on Foreign Types
1.45.0 · sourceimpl Ord for SocketAddrV4
impl Ord for SocketAddrV4
fn cmp(&self, other: &SocketAddrV4) -> Ordering
1.8.0 · sourceimpl Ord for SystemTime
impl Ord for SystemTime
fn cmp(&self, other: &SystemTime) -> Ordering
1.45.0 · sourceimpl Ord for SocketAddrV6
impl Ord for SocketAddrV6
fn cmp(&self, other: &SocketAddrV6) -> Ordering
sourceimpl Ord for SocketAddr
impl Ord for SocketAddr
fn cmp(&self, other: &SocketAddr) -> Ordering
sourceimpl<'_> Ord for PrefixComponent<'_>
impl<'_> Ord for PrefixComponent<'_>
fn cmp(&self, other: &PrefixComponent<'_>) -> Ordering
sourceimpl<'_> Ord for Components<'_>
impl<'_> Ord for Components<'_>
fn cmp(&self, other: &Components<'_>) -> Ordering
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
sourceimpl<A, B, C, D, E, F, G, H, I, J, K> Ord for (A, B, C, D, E, F, G, H, I, J, K) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord,
J: Ord,
K: Ord + ?Sized,
impl<A, B, C, D, E, F, G, H, I, J, K> Ord for (A, B, C, D, E, F, G, H, I, J, K) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord,
J: Ord,
K: Ord + ?Sized,
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
sourceimpl<T, const N: usize> Ord for [T; N] where
T: Ord,
impl<T, const N: usize> Ord for [T; N] where
T: Ord,
Implements comparison of arrays lexicographically.
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
sourceimpl<A, B, C, D, E, F, G, H, I, J> Ord for (A, B, C, D, E, F, G, H, I, J) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord,
J: Ord + ?Sized,
impl<A, B, C, D, E, F, G, H, I, J> Ord for (A, B, C, D, E, F, G, H, I, J) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord,
J: Ord + ?Sized,
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
1.4.0 · sourceimpl<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
sourceimpl<A, B, C, D, E, F, G, H, I, J, K, L> Ord for (A, B, C, D, E, F, G, H, I, J, K, L) where
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,
impl<A, B, C, D, E, F, G, H, I, J, K, L> Ord for (A, B, C, D, E, F, G, H, I, J, K, L) where
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,
sourceimpl<A, B, C, D, E, F, G, H> Ord for (A, B, C, D, E, F, G, H) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord + ?Sized,
impl<A, B, C, D, E, F, G, H> Ord for (A, B, C, D, E, F, G, H) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord + ?Sized,
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
sourceimpl<A, B, C, D, E, F, G> Ord for (A, B, C, D, E, F, G) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord + ?Sized,
impl<A, B, C, D, E, F, G> Ord for (A, B, C, D, E, F, G) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord + ?Sized,
1.4.0 · sourceimpl<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
sourceimpl Ord for str
impl Ord for str
Implements ordering of strings.
Strings are ordered lexicographically by their byte values. This orders Unicode code
points based on their positions in the code charts. This is not necessarily the same as
“alphabetical” order, which varies by language and locale. Sorting strings according to
culturally-accepted standards requires locale-specific data that is outside the scope of
the str
type.
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J) -> Ret
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J) -> Ret
sourceimpl<A, B, C, D, E, F> Ord for (A, B, C, D, E, F) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord + ?Sized,
impl<A, B, C, D, E, F> Ord for (A, B, C, D, E, F) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord + ?Sized,
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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 fn(A, B, C, D, E, F, G, H, I) -> Ret
1.4.0 · sourceimpl<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
sourceimpl<A, B, C, D, E> Ord for (A, B, C, D, E) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord + ?Sized,
impl<A, B, C, D, E> Ord for (A, B, C, D, E) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord + ?Sized,
sourceimpl<A, B, C, D, E, F, G, H, I> Ord for (A, B, C, D, E, F, G, H, I) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord + ?Sized,
impl<A, B, C, D, E, F, G, H, I> Ord for (A, B, C, D, E, F, G, H, I) where
A: Ord,
B: Ord,
C: Ord,
D: Ord,
E: Ord,
F: Ord,
G: Ord,
H: Ord,
I: Ord + ?Sized,
1.4.0 · sourceimpl<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
1.4.0 · sourceimpl<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
sourceimpl<T, A> Ord for Vec<T, A> where
T: Ord,
A: Allocator,
impl<T, A> Ord for Vec<T, A> where
T: Ord,
A: Allocator,
Implements ordering of vectors, lexicographically.