Trait Eq

1.0.0 · 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.

Implementors§

1.0.0 · Source§

Trait EqCopy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for hyperlane::atomic::Ordering

impl Eq for BacktraceStyle

impl Eq for AsciiChar

impl Eq for hyperlane::ContentType

impl Eq for FpCategory

impl Eq for GetManyMutError

impl Eq for hyperlane::HttpVersion

impl Eq for Infallible

impl Eq for IntErrorKind

impl Eq for hyperlane::IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for hyperlane::Methods

impl Eq for hyperlane::Ordering

impl Eq for hyperlane::Protocol

impl Eq for Shutdown

impl Eq for SocketAddr

impl Eq for TryReserveErrorKind

impl Eq for core::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for Sign

impl Eq for BacktraceStatus

impl Eq for VarError

impl Eq for SeekFrom

impl Eq for std::io::error::ErrorKind

impl Eq for TlsProtocolId

impl Eq for AlgorithmId

impl Eq for OperatingMode

impl Eq for KbkdfCtrHmacAlgorithmId

impl Eq for SskdfDigestAlgorithmId

impl Eq for SskdfHmacAlgorithmId

impl Eq for BlockCipherId

impl Eq for KeySize

impl Eq for point_conversion_form_t

impl Eq for BrotliEncoderMode

impl Eq for CodeBlockState

impl Eq for BrotliEncoderOperation

impl Eq for BrotliEncoderStreamState

impl Eq for BrotliEncoderParameter

impl Eq for FlushCompress

impl Eq for FlushDecompress

impl Eq for Status

impl Eq for Compress

impl Eq for http_type::content_type::type::ContentType

impl Eq for http_type::http_version::type::HttpVersion

impl Eq for http_type::methods::type::Methods

impl Eq for http_type::protocol::type::Protocol

impl Eq for TrieType

impl Eq for ExtensionType

impl Eq for Direction

impl Eq for Decomposed

impl Eq for BidiPairingProperties

impl Eq for PropertiesError

impl Eq for GeneralCategory

impl Eq for CheckedBidiPairedBracketType

impl Eq for BufferFormat

impl Eq for DataErrorKind

impl Eq for LocaleFallbackPriority

impl Eq for LocaleFallbackSupplement

impl Eq for DnsLength

impl Eq for ErrorPolicy

impl Eq for Hyphens

impl Eq for ProcessingError

impl Eq for ProcessingSuccess

impl Eq for Level

impl Eq for LevelFilter

impl Eq for CompressionStrategy

impl Eq for TDEFLFlush

impl Eq for TDEFLStatus

impl Eq for miniz_oxide::deflate::CompressionLevel

impl Eq for DataFormat

impl Eq for MZError

impl Eq for MZFlush

impl Eq for MZStatus

impl Eq for TINFLStatus

impl Eq for rustls_pki_types::server_name::IpAddr

Trait Eq

§How can I implement `Eq`?