Trait Eq

1.0.0 (const: unstable) · Source

pub trait Eq: PartialEq { }

Expand description

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
transitive: a == b and b == c implies a == c
consistent: a != b if and only if !(a == b)

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.

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for Action

impl Eq for AriaCurrent

impl Eq for AutoComplete

impl Eq for HasPopup

impl Eq for Invalid

impl Eq for ListStyle

impl Eq for Live

impl Eq for accesskit::Orientation

impl Eq for Role

impl Eq for ScrollHint

impl Eq for ScrollUnit

impl Eq for SortDirection

impl Eq for accesskit::TextAlign

impl Eq for TextDecorationStyle

impl Eq for TextDirection

impl Eq for Toggled

impl Eq for VerticalOffset

impl Eq for AhoCorasickKind

impl Eq for aho_corasick::packed::api::MatchKind

impl Eq for aho_corasick::util::error::MatchErrorKind

impl Eq for aho_corasick::util::search::Anchored

impl Eq for aho_corasick::util::search::MatchKind

impl Eq for StartKind

impl Eq for allocator_api2::stable::raw_vec::TryReserveErrorKind

impl Eq for arraystring::error::Error

impl Eq for base64::alphabet::ParseAlphabetError

impl Eq for base64::alphabet::ParseAlphabetError

impl Eq for base64::decode::DecodeError

impl Eq for base64::decode::DecodeError

impl Eq for base64::decode::DecodeSliceError

impl Eq for base64::decode::DecodeSliceError

impl Eq for base64::encode::EncodeSliceError

impl Eq for base64::encode::EncodeSliceError

impl Eq for base64::engine::DecodePaddingMode

impl Eq for base64::engine::DecodePaddingMode

impl Eq for CheckedCastError

impl Eq for PodCastError

impl Eq for byteorder::BigEndian

impl Eq for byteorder::LittleEndian

impl Eq for byteorder_lite::BigEndian

impl Eq for byteorder_lite::LittleEndian

impl Eq for Keviyah

impl Eq for StartOfYear

impl Eq for YearType

impl Eq for cobs::dec::DecodeError

impl Eq for LabelStyle

impl Eq for codespan_reporting::diagnostic::Severity

impl Eq for ColorSpaceLayout

impl Eq for color::parse::ParseError

impl Eq for ColorSpaceTag

impl Eq for CheckResult

impl Eq for Destination

impl Eq for HashAlgorithm

impl Eq for Initiator

impl Eq for InlineCheckType

impl Eq for MatchResult

impl Eq for NavigationCheckType

impl Eq for ParserMetadata

impl Eq for PolicyDisposition

impl Eq for PolicySource

impl Eq for SubresourceIntegrityMetadata

impl Eq for Violates

impl Eq for ViolationResource

impl Eq for cookie::draft::SameSite

impl Eq for cookie::expiration::Expiration

impl Eq for cookie::expiration::Expiration

impl Eq for cookie::parse::ParseError

impl Eq for cookie::parse::ParseError

impl Eq for cookie::same_site::SameSite

impl Eq for crossbeam_channel::err::RecvTimeoutError

impl Eq for crossbeam_channel::err::TryRecvError

impl Eq for cssparser::color::PredefinedColorSpace

impl Eq for TokenSerializationType

impl Eq for AncestorData

Trait Eq

§How can I implement `Eq`?