Trait Eq

1.6.0 (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 DecodeError

impl Eq for hashbrown::TryReserveError

impl Eq for hashbrown::TryReserveError

impl Eq for indexmap::GetDisjointMutError

impl Eq for Level

impl Eq for LevelFilter

impl Eq for AddressSize

impl Eq for object::common::Architecture

impl Eq for object::common::BinaryFormat

impl Eq for ComdatKind

impl Eq for FileFlags

impl Eq for RelocationEncoding

impl Eq for RelocationFlags

impl Eq for RelocationKind

impl Eq for SectionFlags

impl Eq for SectionKind

impl Eq for object::common::SegmentFlags

impl Eq for SubArchitecture

impl Eq for SymbolKind

impl Eq for SymbolScope

impl Eq for object::endian::Endianness

impl Eq for ArchiveKind

impl Eq for ImportType

impl Eq for CompressionFormat

impl Eq for FileKind

impl Eq for ObjectKind

impl Eq for object::read::RelocationTarget

impl Eq for object::read::SymbolSection

impl Eq for CoffExportStyle

impl Eq for Mangling

impl Eq for StandardSection

impl Eq for StandardSegment

impl Eq for object::write::SymbolSection

impl Eq for postcard::error::Error

impl Eq for CDataModel

impl Eq for Size

impl Eq for ParseError

impl Eq for Aarch64Architecture

impl Eq for target_lexicon::targets::Architecture

impl Eq for ArmArchitecture

impl Eq for target_lexicon::targets::BinaryFormat

impl Eq for CustomVendor

impl Eq for Environment

impl Eq for Mips32Architecture

impl Eq for Mips64Architecture

impl Eq for OperatingSystem

impl Eq for Riscv32Architecture

impl Eq for Riscv64Architecture

impl Eq for target_lexicon::targets::Vendor

impl Eq for X86_32Architecture

impl Eq for CallingConvention

impl Eq for target_lexicon::triple::Endianness

impl Eq for PointerWidth

impl Eq for zerocopy::byteorder::BigEndian

impl Eq for zerocopy::byteorder::LittleEndian

impl Eq for ConstOp

impl Eq for EngineOrModuleTypeIndex

impl Eq for EntityIndex

impl Eq for wasmtime_environ::RelocationTarget

impl Eq for Trap

impl Eq for VMGcKind

impl Eq for WasmCompositeType

impl Eq for WasmHeapTopType

impl Eq for WasmHeapType

impl Eq for WasmStorageType

impl Eq for WasmValType

impl Eq for LibCall

impl Eq for AbstractHeapType

impl Eq for BlockType

impl Eq for CanonicalFunction

impl Eq for CanonicalOption

impl Eq for Catch

impl Eq for ComdatSymbolKind

impl Eq for ComponentExternalKind

Trait Eq

§How can I implement `Eq`?