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".

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for otter_nodejs_tests::base64::DecodeError

impl Eq for otter_nodejs_tests::bundles::Kind

impl Eq for otter_nodejs_tests::chrono::Month

impl Eq for RoundingError

impl Eq for SecondsFormat

impl Eq for otter_nodejs_tests::chrono::Weekday

impl Eq for Colons

impl Eq for Fixed

impl Eq for Numeric

impl Eq for OffsetPrecision

impl Eq for Pad

impl Eq for ParseErrorKind

impl Eq for otter_nodejs_tests::chrono_tz::Tz

impl Eq for AccountScope

impl Eq for otter_nodejs_tests::BigEndian

impl Eq for otter_nodejs_tests::ErrorKind

impl Eq for Infallible

impl Eq for otter_nodejs_tests::IpAddr

impl Eq for LinkKind

impl Eq for otter_nodejs_tests::LittleEndian

impl Eq for VersionError

impl Eq for OccDisplacement

impl Eq for OccultationKindAlwaysOk

impl Eq for OldNewIndex

impl Eq for otter_nodejs_tests::Ordering

impl Eq for PieceMoveable

impl Eq for PieceOpErrorPartiallyProcessed

impl Eq for PresentationLayout

impl Eq for ProgressUpdateMode

impl Eq for Shape

impl Eq for SocketAddr

impl Eq for TablePermission

impl Eq for VarError

impl Eq for WriteStyle

impl Eq for otter_nodejs_tests::env_logger::fmt::Color

impl Eq for otter_nodejs_tests::flexi_logger::Level

impl Eq for otter_nodejs_tests::flexi_logger::LevelFilter

impl Eq for WriteMode

impl Eq for otter_nodejs_tests::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for otter_nodejs_tests::fmt::Sign

impl Eq for AsciiChar

impl Eq for CharCase

impl Eq for FromBytesWithNulError

impl Eq for Locality

impl Eq for AtomicOrdering

impl Eq for SimdAlign

impl Eq for Ipv6MulticastScope

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for otter_nodejs_tests::inventory::core::slice::GetDisjointMutError

impl Eq for otter_nodejs_tests::inventory::core::sync::atomic::Ordering

impl Eq for otter_nodejs_tests::io::SeekFrom

impl Eq for tpacket_versions

impl Eq for RecvTimeoutError

impl Eq for otter_nodejs_tests::mpsc::TryRecvError

impl Eq for otter_nodejs_tests::nix::dir::Type

impl Eq for otter_nodejs_tests::nix::errno::Errno

impl Eq for FlockArg

impl Eq for PosixFadviseAdvice

impl Eq for AioCancelStat

impl Eq for AioFsyncMode

impl Eq for LioMode

impl Eq for LioOpcode

impl Eq for EpollOp

impl Eq for MmapAdvise

impl Eq for otter_nodejs_tests::nix::sys::ptrace::Event

impl Eq for otter_nodejs_tests::nix::sys::ptrace::Request

impl Eq for QuotaFmt

impl Eq for QuotaType

impl Eq for RebootMode

impl Eq for Resource

impl Eq for SigHandler

impl Eq for SigevNotify

Trait Eq

§How can I implement `Eq`?