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 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.

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for RtlError

impl Eq for AsciiChar

impl Eq for sails_rs::prelude::collections::TryReserveErrorKind

impl Eq for sails_rs::prelude::collections::hashbrown::TryReserveError

impl Eq for Infallible

impl Eq for ErrorReplyReason

impl Eq for ReplyCode

impl Eq for SignalCode

impl Eq for SimpleExecutionError

impl Eq for SimpleUnavailableActorError

impl Eq for SuccessReplyReason

impl Eq for FromBytesWithNulError

impl Eq for sails_rs::prelude::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for Sign

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for GetDisjointMutError

impl Eq for SearchStep

impl Eq for sails_rs::prelude::cmp::Ordering

impl Eq for AtomicOrdering

impl Eq for SimdAlign

impl Eq for IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

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

impl Eq for BacktraceStatus

impl Eq for VarError

impl Eq for SeekFrom

impl Eq for ErrorKind

impl Eq for Shutdown

impl Eq for BacktraceStyle

impl Eq for RecvTimeoutError

impl Eq for TryRecvError

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

impl Eq for bs58::alphabet::Error

impl Eq for bs58::decode::Error

impl Eq for bs58::encode::Error

impl Eq for byte_slice_cast::Error

impl Eq for CheckedCastError

impl Eq for PodCastError

impl Eq for BigEndian

impl Eq for LittleEndian

impl Eq for PollNext

impl Eq for gcore::errors::Error

impl Eq for ExecutionError

impl Eq for ExtError

impl Eq for MemoryError

impl Eq for MessageError

impl Eq for ReservationError

impl Eq for gear_ss58::Error

impl Eq for ConversionError

impl Eq for gstd::common::errors::Error

impl Eq for UsageError

impl Eq for hashbrown::TryReserveError

impl Eq for primitive_types::Error

impl Eq for primitive_types::Error

impl Eq for BernoulliError

impl Eq for WeightedError

impl Eq for DecodeError

impl Eq for Unexpected

impl Eq for Kind

impl Eq for MetaForm

impl Eq for PortableForm

impl Eq for TypeDefPrimitive

impl Eq for PathError

impl Eq for BitsOrderFormat

impl Eq for BitsStoreFormat

impl Eq for Primitive

impl Eq for UnhandledKind

impl Eq for FromDecStrErr

impl Eq for uint::uint::FromStrRadixErrKind

impl Eq for uint::uint::FromStrRadixErrKind

impl Eq for bool

Trait Eq

§How can I implement `Eq`?