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".

Implementors§

1.100.0 (const: unstable) · Source§

impl Eq for !

1.0.0 (const: unstable) · Source§

Eq

Trait Eq Copy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for !

impl Eq for ()

impl Eq for Abi

impl Eq for AccessError

impl Eq for core::net::parser::AddrParseError

impl Eq for rustls_pki_types::server_name::AddrParseError

impl Eq for AlertDescription

impl Eq for ring::aead::algorithm::Algorithm

impl Eq for ring::aead::quic::Algorithm

impl Eq for ring::agreement::Algorithm

impl Eq for ring::digest::Algorithm

impl Eq for ring::hkdf::Algorithm

impl Eq for ring::hmac::Algorithm

impl Eq for ring::pbkdf2::Algorithm

impl Eq for AlgorithmIdentifier

impl Eq for http_request::mem::Alignment

impl Eq for http_request::self::Alignment

impl Eq for AllocError

impl Eq for AsciiChar

impl Eq for AsciiDenyList

impl Eq for AsciiProbeResult

impl Eq for AsciiSet

impl Eq for Assume

impl Eq for AtomicOrdering

impl Eq for http_type::attribute::enum::Attribute

impl Eq for icu_locale_core::extensions::unicode::attribute::Attribute

impl Eq for Attributes

impl Eq for BacktraceStatus

impl Eq for BacktraceStyle

impl Eq for BernoulliError

impl Eq for BidiClass

impl Eq for BidiMirroringGlyph

impl Eq for BidiPairedBracketType

impl Eq for Body

impl Eq for BrotliEncoderMode

impl Eq for BrotliEncoderOperation

impl Eq for BrotliEncoderParameter

impl Eq for BrotliEncoderStreamState

impl Eq for BufferFormat

impl Eq for ByteStr

impl Eq for ByteString

impl Eq for Bytes

impl Eq for BytesMut

impl Eq for CStr

impl Eq for CString

impl Eq for CalendarAlgorithm

impl Eq for CanonicalCombiningClass

impl Eq for Category

impl Eq for CertificateCompressionAlgorithm

impl Eq for CertificateType

impl Eq for ChaCha8Rng

impl Eq for ChaCha12Rng

impl Eq for ChaCha20Rng

impl Eq for CharCase

impl Eq for CharTryFromError

impl Eq for CharULE

impl Eq for CipherSuite

impl Eq for CodeBlockState

impl Eq for CodePointInversionListAndStringListULE

impl Eq for CodePointInversionListULE

impl Eq for CodePointTrieHeader

impl Eq for CollationCaseFirst

impl Eq for CollationNumericOrdering

impl Eq for CollationType

impl Eq for CommonVariantType

impl Eq for Components<'_>

impl Eq for Compress

impl Eq for Compression

impl Eq for miniz_oxide::deflate::CompressionLevel

impl Eq for rustls::compress::CompressionLevel

impl Eq for CompressionStrategy

impl Eq for http_request::ContentType

impl Eq for rustls::enums::ContentType

impl Eq for Cookie

Trait Eq

§How can I implement `Eq`?