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 datex_core::ast::error::pattern::Pattern

impl Eq for datex_core::ast::lexer::Token

impl Eq for StaticValueOrDXB

impl Eq for VariableModel

impl Eq for VariableRepresentation

impl Eq for Formatting

impl Eq for ScopeType

impl Eq for InstructionCode

impl Eq for InternalSlot

impl Eq for TypeSpaceInstructionCode

impl Eq for CoreLibPointerId

impl Eq for InterfacePriority

impl Eq for ComInterfaceState

impl Eq for MediaKind

impl Eq for Reference

impl Eq for ReferenceCreationError

impl Eq for ReferenceMutability

impl Eq for InvalidProgramError

impl Eq for CollectionTypeDefinition

impl Eq for TypeDefinition

impl Eq for StructuralTypeDefinition

impl Eq for TypeContainer

impl Eq for CoreValue

impl Eq for Decimal

impl Eq for DecimalTypeVariant

impl Eq for TypedDecimal

impl Eq for EndpointInstance

impl Eq for EndpointType

impl Eq for NumberParseError

impl Eq for IntegerTypeVariant

impl Eq for TypedInteger

impl Eq for datex_core::values::core_values::map::Map

impl Eq for PointerAddress

impl Eq for ValueContainer

impl Eq for AsciiChar

impl Eq for datex_core::without_std::collections::TryReserveErrorKind

impl Eq for Infallible

impl Eq for FromBytesWithNulError

impl Eq for datex_core::without_std::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for datex_core::without_std::fmt::Sign

impl Eq for AtomicOrdering

impl Eq for datex_core::without_std::net::IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for datex_core::without_std::slice::GetDisjointMutError

impl Eq for SearchStep

impl Eq for datex_core::without_std::sync::atomic::Ordering

impl Eq for datex_core::without_std::cmp::Ordering

impl Eq for BacktraceStatus

impl Eq for VarError

impl Eq for SeekFrom

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

impl Eq for std::net::Shutdown

impl Eq for BacktraceStyle

impl Eq for RecvTimeoutError

impl Eq for std::sync::mpsc::TryRecvError

impl Eq for AhoCorasickKind

impl Eq for aho_corasick::packed::api::MatchKind

impl Eq for aho_corasick::util::error::MatchErrorKind

impl Eq for aho_corasick::util::search::Anchored

impl Eq for aho_corasick::util::search::MatchKind

impl Eq for aho_corasick::util::search::StartKind

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

impl Eq for CharSet

impl Eq for IndexType

impl Eq for LabelAttach

impl Eq for Explicit

impl Eq for Implicit

impl Eq for asn1_rs::class::Class

impl Eq for ASN1TimeZone

impl Eq for DerConstraint

Trait Eq

§How can I implement `Eq`?