Trait Eq

1.0.0 · Source

pub trait Eq: PartialEq { }

Expand description

core Trait for comparisons corresponding to equivalence relations.

The primary difference to PartialEq is the additional requirement for reflexivity. A type that implements PartialEq guarantees that for all a, b and c:

symmetric: a == b implies b == a and a != b implies !(a == b)
transitive: a == b and b == c implies a == c

Eq, which builds on top of PartialEq also implies:

reflexive: a == a

This property cannot be checked by the compiler, and therefore Eq is a trait without methods.

Violating this property 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.

Floating point types such as f32 and f64 implement only PartialEq but not Eq because NaN != NaN.

§Derivable

This trait can be used with #[derive]. When derived, because Eq has no extra methods, it is only informing the compiler that this is an equivalence relation rather than a partial equivalence relation. Note that the derive strategy requires all fields are Eq, which isn’t always desired.

§How can I implement `Eq`?

If you cannot use the derive strategy, specify that your type implements Eq, which has no extra methods:

enum BookFormat {
    Paperback,
    Hardback,
    Ebook,
}

struct Book {
    isbn: i32,
    format: BookFormat,
}

impl PartialEq for Book {
    fn eq(&self, other: &Self) -> bool {
        self.isbn == other.isbn
    }
}

impl Eq for Book {}

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Trait EqCopy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for devela::_core::ascii::Char

impl Eq for FromBytesWithNulError

impl Eq for DebugAsHex

impl Eq for devela::_core::fmt::Sign

impl Eq for AtomicOrdering

impl Eq for Ipv6MulticastScope

impl Eq for devela::_core::slice::GetDisjointMutError

impl Eq for SearchStep

impl Eq for devela::_dep::_alloc::collections::TryReserveErrorKind

impl Eq for SeekFrom

impl Eq for BacktraceStyle

impl Eq for devela::_dep::allocator_api2::collections::TryReserveErrorKind

impl Eq for CollectionAllocErr

impl Eq for CheckedCastError

impl Eq for PodCastError

impl Eq for SetCursorStyle

impl Eq for devela::_dep::crossterm::event::Event

impl Eq for devela::_dep::crossterm::event::KeyCode

impl Eq for KeyEventKind

impl Eq for MediaKeyCode

impl Eq for ModifierKeyCode

impl Eq for devela::_dep::crossterm::event::MouseButton

impl Eq for MouseEventKind

impl Eq for Attribute

impl Eq for devela::_dep::crossterm::style::Color

impl Eq for Colored

impl Eq for ClearType

impl Eq for devela::_dep::ffmpeg_the_third::codec::encoder::Comparison

impl Eq for Decision

impl Eq for MotionEstimation

impl Eq for Compliance

impl Eq for devela::_dep::ffmpeg_the_third::codec::Id

impl Eq for Profile

impl Eq for devela::_dep::ffmpeg_the_third::codec::packet::side_data::Type

impl Eq for AAC

impl Eq for DTS

impl Eq for H264

impl Eq for HEVC

impl Eq for JPEG2000

impl Eq for MPEG2

impl Eq for MPEG4

impl Eq for VC1

impl Eq for VP9

impl Eq for devela::_dep::ffmpeg_the_third::codec::subtitle::Type

impl Eq for devela::_dep::ffmpeg_the_third::codec::threading::Type

impl Eq for AudioService

impl Eq for Channel

impl Eq for ChannelOrder

impl Eq for Discard

impl Eq for devela::_dep::ffmpeg_the_third::Error

impl Eq for FieldOrder

impl Eq for Rounding

impl Eq for Pixel

impl Eq for Sample

impl Eq for devela::_dep::ffmpeg_the_third::software::resampling::Dither

impl Eq for Engine

impl Eq for Filter

impl Eq for devela::_dep::ffmpeg_the_third::software::scaling::ColorSpace

impl Eq for AVActiveFormatDescription

impl Eq for AVAppToDevMessageType

impl Eq for AVAudioServiceType

impl Eq for AVCRCId

impl Eq for AVChannel

impl Eq for AVChannelOrder

impl Eq for AVChromaLocation

impl Eq for AVClassCategory

impl Eq for AVCodecID

impl Eq for AVColorPrimaries

impl Eq for AVColorRange

impl Eq for AVColorSpace

impl Eq for AVColorTransferCharacteristic

impl Eq for AVDevToAppMessageType

impl Eq for AVDiscard

impl Eq for AVDownmixType

impl Eq for AVDurationEstimationMethod

Trait Eq

§How can I implement `Eq`?