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.

Trait EqCopy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for PrivateInput

impl Eq for Dictionary

impl Eq for OffsetValue

impl Eq for BuiltinName

impl Eq for ApUpdate

impl Eq for FpUpdate

impl Eq for Op1Addr

impl Eq for Opcode

impl Eq for PcUpdate

impl Eq for Register

impl Eq for Res

impl Eq for LayoutName

impl Eq for MaybeRelocatable

impl Eq for CairoPieValidationError

impl Eq for ExecScopeError

impl Eq for InsufficientAllocatedCellsError

impl Eq for BuiltinAdditionalData

impl Eq for CairoArg

impl Eq for cairo_vm::with_std::cmp::Ordering

impl Eq for Infallible

impl Eq for cairo_vm::with_std::fmt::Alignment

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for SearchStep

impl Eq for cairo_vm::with_std::sync::atomic::Ordering

impl Eq for RecvTimeoutError

impl Eq for TryRecvError

impl Eq for alloc::collections::TryReserveErrorKind

impl Eq for AsciiChar

impl Eq for IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

impl Eq for BacktraceStatus

impl Eq for VarError

impl Eq for SeekFrom

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

impl Eq for Shutdown

impl Eq for BacktraceStyle

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

impl Eq for LegendreSymbol

impl Eq for Compress

impl Eq for Validate

impl Eq for ark_std::io::error::ErrorKind

impl Eq for AllowedEnumVariants

impl Eq for IntegerType

impl Eq for BigEndian

impl Eq for LittleEndian

impl Eq for FlushCompress

impl Eq for FlushDecompress

impl Eq for Status

impl Eq for hashbrown::TryReserveError

impl Eq for EllipticCurveError

impl Eq for ByteConversionError

impl Eq for CreationError

impl Eq for DeserializationError

impl Eq for PairingError

impl Eq for CompressionStrategy

impl Eq for TDEFLFlush

impl Eq for TDEFLStatus

impl Eq for CompressionLevel

impl Eq for DataFormat

impl Eq for MZError

impl Eq for MZFlush

impl Eq for MZStatus

impl Eq for TINFLStatus

impl Eq for nom::error::ErrorKind

impl Eq for Needed

impl Eq for Endianness

impl Eq for Sign

impl Eq for BernoulliError

impl Eq for WeightedError

impl Eq for RoundingStrategy

impl Eq for Category

impl Eq for Value

impl Eq for CurveError

Trait Eq

§How can I implement `Eq`?