devela::_dep::_std::cmp

Trait Eq

1.0.0 · Source

pub trait Eq: PartialEq { }

Available on crate feature std only.

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 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 DebugAsHex

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

impl Eq for IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

impl Eq for GetManyMutError

impl Eq for SearchStep

impl Eq for ExampleEnumIntU8

impl Eq for AngleDirection

impl Eq for AngleKind

impl Eq for AudioError

impl Eq for BacktraceStatus

impl Eq for ColorError

impl Eq for CompressionMode

impl Eq for DrawError

impl Eq for EncodingMode

impl Eq for devela::all::FmtAlignment

impl Eq for FontError

impl Eq for ImageError

impl Eq for devela::all::IoErrorKind

impl Eq for MediaError

impl Eq for MidiError

impl Eq for NotAvailable

impl Eq for WaveletUnitRole

impl Eq for Infallible

impl Eq for DataNotEnough

impl Eq for MismatchedBounds

impl Eq for PartialSpace

impl Eq for FpCategory

impl Eq for NumError

impl Eq for devela::num::Ordering

impl Eq for devela::num::Sign

impl Eq for UnitBi

impl Eq for UnitSi

impl Eq for Month

impl Eq for devela::phys::Weekday

impl Eq for devela::text::AsciiChar

impl Eq for InvalidText

impl Eq for IntErrorKind

impl Eq for devela::ui::LayoutError

impl Eq for devela::work::AtomicOrdering

impl Eq for TryReserveErrorKind

impl Eq for CollectionAllocErr

impl Eq for CheckedCastError

impl Eq for PodCastError

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 Color

impl Eq for Colored

impl Eq for ClearType

impl Eq for devela::_dep::hashbrown::TryReserveError

impl Eq for Era

impl Eq for devela::_dep::jiff::civil::Weekday

impl Eq for RoundMode

impl Eq for Unit

impl Eq for Meridiem

impl Eq for PiecesOffset

impl Eq for AmbiguousOffset

impl Eq for Dst

impl Eq for EqFilterKind

impl Eq for WhenToStart

impl Eq for PlaybackState

impl Eq for TrackPlaybackState

impl Eq for devela::_dep::log::Level

impl Eq for devela::_dep::log::LevelFilter

impl Eq for ConnectErrorKind

impl Eq for Ignore

impl Eq for PortInfoError

Trait Eq

§How can I implement `Eq`?