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 AsciiChar

impl Eq for TryReserveErrorKind

impl Eq for Infallible

impl Eq for VarError

impl Eq for origin_studio::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for Sign

impl Eq for origin_studio::io::SeekFrom

impl Eq for IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for GetDisjointMutError

impl Eq for SearchStep

impl Eq for origin_studio::sync::atomic::Ordering

impl Eq for origin_studio::cmp::Ordering

impl Eq for FromBytesWithNulError

impl Eq for DwarfFileType

impl Eq for Format

impl Eq for SectionId

impl Eq for Vendor

impl Eq for RunTimeEndian

impl Eq for Pointer

impl Eq for gimli::read::Error

impl Eq for IndexSectionId

impl Eq for ValueType

impl Eq for fsconfig_command

impl Eq for membarrier_cmd

impl Eq for membarrier_cmd_flag

impl Eq for procmap_query_flags

impl Eq for rustix::backend::fs::types::Advice

impl Eq for FileType

impl Eq for FlockOperation

impl Eq for rustix::backend::mm::types::Advice

impl Eq for Resource

impl Eq for MembarrierCommand

impl Eq for TimerfdClockId

impl Eq for ClockId

impl Eq for rustix::fs::seek_from::SeekFrom

impl Eq for Direction

impl Eq for DumpableBehavior

impl Eq for EndianMode

impl Eq for FloatingPointMode

impl Eq for MachineCheckMemoryCorruptionKillPolicy

impl Eq for PTracer

impl Eq for SpeculationFeature

impl Eq for TimeStampCounterReadability

impl Eq for TimingMethod

impl Eq for VirtualMemoryMapAddress

impl Eq for FlockOffsetType

impl Eq for FlockType

impl Eq for WakeOp

impl Eq for WakeOpCmp

impl Eq for Capability

impl Eq for CoreSchedulingScope

impl Eq for SecureComputingMode

impl Eq for SysCallUserDispatchFastSwitch

impl Eq for LinkNameSpaceType

impl Eq for bool

impl Eq for char

impl Eq for i8

impl Eq for i16

impl Eq for i32

impl Eq for i64

impl Eq for i128

impl Eq for isize

impl Eq for !

impl Eq for str

impl Eq for u8

impl Eq for u16

impl Eq for u32

impl Eq for u64

impl Eq for u128

impl Eq for ()

Trait Eq

§How can I implement `Eq`?