Trait script::dom::bindings::import::module::cmp::Ord

1.0.0 · source ·

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

    // Provided methods
    fn max(self, other: Self) -> Self
       where Self: Sized { ... }
    fn min(self, other: Self) -> Self
       where Self: Sized { ... }
    fn clamp(self, min: Self, max: Self) -> Self
       where Self: Sized + 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.

Violating these requirements is a logic error. The behavior resulting from a logic error is not specified, but users of the trait must ensure that such logic errors do not result in undefined behavior. This means that unsafe code must not rely on the correctness of these methods.

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 >.

Derivable

This trait can be used with #[derive].

When derived on structs, it will produce a lexicographic ordering based on the top-to-bottom declaration order of the struct’s members.

When derived 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§

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.

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§

1.21.0 · source

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

Compares and returns the maximum of two values.

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

Examples

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

1.21.0 · source

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

Compares and returns the minimum of two values.

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

Examples

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

1.50.0 · source

fn clamp(self, min: Self, max: Self) -> Selfwhere Self: Sized + 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.

Panics

Panics if min > max.

Examples

assert_eq!((-3).clamp(-2, 1), -2);
assert_eq!(0.clamp(-2, 1), 0);
assert_eq!(2.clamp(-2, 1), 1);

Trait script::dom::bindings::import::module::cmp::Ord

Required Methods§

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

Provided Methods§

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

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

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

Implementors§

impl Ord for BigEndian

impl Ord for LittleEndian

impl Ord for Month

impl Ord for Meaning

impl Ord for SectionId

impl Ord for ColumnType

impl Ord for AttrValueKind

impl Ord for DoctypeIdKind

impl Ord for RawKind

impl Ord for ScriptEscapeKind

impl Ord for html5ever::tokenizer::states::State

impl Ord for ExtensionType

impl Ord for LocaleFallbackPriority

impl Ord for LocaleFallbackSupplement

impl Ord for log::Level

impl Ord for log::LevelFilter

impl Ord for AddressSpace

impl Ord for ArraySize

impl Ord for AtomicFunction

impl Ord for BinaryOperator

impl Ord for naga::BuiltIn

impl Ord for ConservativeDepth

impl Ord for DerivativeAxis

impl Ord for DerivativeControl

impl Ord for ImageClass

impl Ord for ImageDimension

impl Ord for Interpolation

impl Ord for MathFunction

impl Ord for RelationalFunction

impl Ord for Sampling

impl Ord for ScalarKind

impl Ord for ShaderStage

impl Ord for StorageFormat

impl Ord for UnaryOperator

impl Ord for VectorSize

impl Ord for petgraph::Direction

impl Ord for ProfilerCategory

impl Ord for TimerMetadataFrameType

impl Ord for TimerMetadataReflowType

impl Ord for Channels

impl Ord for ColorSpace

impl Ord for Utf8Sequence

impl Ord for ron::value::Number

impl Ord for ron::value::Value

impl Ord for rustix::ioctl::Direction

impl Ord for SocketAddrAny

impl Ord for Void

impl Ord for ParamDir

impl Ord for ParamType

impl Ord for AccessQualifier

impl Ord for AddressingModel

impl Ord for spirv::BuiltIn

impl Ord for CLOp

impl Ord for Capability

impl Ord for Decoration

impl Ord for Dim

impl Ord for ExecutionMode

impl Ord for ExecutionModel

impl Ord for FPRoundingMode

impl Ord for FunctionParameterAttribute

impl Ord for GLOp

impl Ord for GroupOperation

impl Ord for ImageChannelDataType

impl Ord for ImageChannelOrder

impl Ord for ImageFormat

impl Ord for KernelEnqueueFlags

impl Ord for LinkageType

impl Ord for MemoryModel

impl Ord for Op

impl Ord for RayQueryCandidateIntersectionType

impl Ord for RayQueryCommittedIntersectionType

impl Ord for RayQueryIntersection