Trait std::cmp::Ord

1.0.0 · source ·

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
  where
    Self: PartialOrd<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 or a > b is true; and
< is transitive: a < b and b < c implies a < c. The same must hold for both == and >.

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.

Required Methods

source

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.

Provided Methods

1.21.0 · source

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

Compares and returns the maximum of two values.

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

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

Compares and returns the minimum of two values.

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

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

Restrict a value to a certain interval.

Returns max if self is greater than max, and min if self is less than min. Otherwise this returns self.

Implementors

1.34.0 · source

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.

const: unstable · source