Trait std::cmp::Eq
pub trait Eq: PartialEq { }Trait for comparisons corresponding to equivalence relations.
This means, that in addition to a == b and a != b being strict inverses, the relation must be (for all a, b and c):
- reflexive:
a == a; - symmetric:
a == bimpliesb == a(required byPartialEqas well); and - transitive:
a == bandb == cimpliesa == c(required byPartialEqas well).
This property cannot be checked by the compiler, and therefore Eq implies PartialEq, and has no extra 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.
Implement Eq in addition to PartialEq if it’s guaranteed that PartialEq::eq(a, a) always returns true (reflexivity), in addition to the symmetric and transitive properties already required by PartialEq.
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 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 {}Object Safety
This trait is not object safe.
Implementors
impl Eq for AsciiCharimpl Eq for BacktraceStatusimpl Eq for TryReserveErrorKindimpl Eq for Infallibleimpl Eq for VarErrorimpl Eq for std::fmt::Alignmentimpl Eq for ErrorKindimpl Eq for SeekFromimpl Eq for IpAddrimpl Eq for Ipv6MulticastScopeimpl Eq for Shutdownimpl Eq for SocketAddrimpl Eq for FpCategoryimpl Eq for IntErrorKindimpl Eq for BacktraceStyleimpl Eq for Whichimpl Eq for SearchStepimpl Eq for std::sync::atomic::Orderingimpl Eq for RecvTimeoutErrorimpl Eq for TryRecvErrorimpl Eq for std::cmp::Orderingimpl Eq for boolimpl Eq for charimpl Eq for i8impl Eq for i16impl Eq for i32impl Eq for i64impl Eq for i128impl Eq for isizeimpl Eq for !impl Eq for strimpl Eq for u8impl Eq for u16impl Eq for u32impl Eq for u64impl Eq for u128impl Eq for ()impl Eq for usizeimpl Eq for CpuidResultimpl Eq for AllocErrorimpl Eq for Layoutimpl Eq for LayoutErrorimpl Eq for TypeIdimpl Eq for CharTryFromErrorimpl Eq for DecodeUtf16Errorimpl Eq for ParseCharErrorimpl Eq for TryFromCharErrorimpl Eq for TryReserveErrorimpl Eq for CStrimpl Eq for CStringimpl Eq for FromBytesUntilNulErrorimpl Eq for FromBytesWithNulErrorimpl Eq for FromVecWithNulErrorimpl Eq for IntoStringErrorimpl Eq for NulErrorimpl Eq for OsStrimpl Eq for OsStringimpl Eq for Errorimpl Eq for FileTypeimpl Eq for Permissionsimpl Eq for PhantomPinnedimpl Eq for Assumeimpl Eq for AddrParseErrorimpl Eq for Ipv4Addrimpl Eq for Ipv6Addrimpl Eq for SocketAddrV4impl Eq for SocketAddrV6impl Eq for NonZeroI8impl Eq for NonZeroI16impl Eq for NonZeroI32impl Eq for NonZeroI64impl Eq for NonZeroI128impl Eq for NonZeroIsizeimpl Eq for NonZeroU8impl Eq for NonZeroU16impl Eq for NonZeroU32impl Eq for NonZeroU64impl Eq for NonZeroU128impl Eq for NonZeroUsizeimpl Eq for ParseFloatErrorimpl Eq for ParseIntErrorimpl Eq for TryFromIntErrorimpl Eq for RangeFullimpl Eq for UCredAvailable on Unix only.impl Eq for InvalidHandleErrorAvailable on Windows only.impl Eq for NullHandleErrorAvailable on Windows only.impl Eq for Components<'_>impl Eq for Pathimpl Eq for PathBufimpl Eq for StripPrefixErrorimpl Eq for ExitStatusimpl Eq for ExitStatusErrorimpl Eq for Outputimpl Eq for std::ptr::Alignmentimpl Eq for ParseBoolErrorimpl Eq for Utf8Errorimpl Eq for FromUtf8Errorimpl Eq for Stringimpl Eq for RecvErrorimpl Eq for WaitTimeoutResultimpl Eq for AccessErrorimpl Eq for ThreadIdimpl Eq for Durationimpl Eq for Instantimpl Eq for SystemTimeimpl Eq for TryFromFloatSecsErrorimpl<'a> Eq for Component<'a>impl<'a> Eq for Prefix<'a>impl<'a> Eq for Location<'a>impl<'a> Eq for PrefixComponent<'a>impl<'a> Eq for Utf8Chunk<'a>impl<A> Eq for &A
where
A: Eq + ?Sized,impl<A> Eq for &mut A
where
A: Eq + ?Sized,impl<B> Eq for Cow<'_, B>
where
B: Eq + ToOwned + ?Sized,impl<B, C> Eq for ControlFlow<B, C>
where
B: Eq,
C: Eq,impl<Dyn> Eq for DynMetadata<Dyn>
where
Dyn: ?Sized,impl<F> Eq for F
where
F: FnPtr,impl<H> Eq for BuildHasherDefault<H>impl<Idx> Eq for Range<Idx>
where
Idx: Eq,impl<Idx> Eq for RangeFrom<Idx>
where
Idx: Eq,impl<Idx> Eq for RangeInclusive<Idx>
where
Idx: Eq,impl<Idx> Eq for RangeTo<Idx>
where
Idx: Eq,impl<Idx> Eq for RangeToInclusive<Idx>
where
Idx: Eq,impl<K, V, A> Eq for BTreeMap<K, V, A>
where
K: Eq,
V: Eq,
A: Allocator + Clone,impl<K, V, S> Eq for HashMap<K, V, S>
where
K: Eq + Hash,
V: Eq,
S: BuildHasher,impl<P> Eq for Pin<P>
where
P: Deref,
<P as Deref>::Target: Eq,impl<T> Eq for Bound<T>
where
T: Eq,impl<T> Eq for Option<T>
where
T: Eq,impl<T> Eq for Poll<T>
where
T: Eq,impl<T> Eq for *const T
where
T: ?Sized,impl<T> Eq for *mut T
where
T: ?Sized,impl<T> Eq for [T]
where
T: Eq,impl<T> Eq for (T₁, T₂, …, Tₙ)
where
T: Eq + ?Sized,This trait is implemented for tuples up to twelve items long.
impl<T> Eq for Cell<T>
where
T: Eq + Copy,impl<T> Eq for OnceCell<T>
where
T: Eq,impl<T> Eq for RefCell<T>
where
T: Eq + ?Sized,impl<T> Eq for PhantomData<T>
where
T: ?Sized,impl<T> Eq for Discriminant<T>impl<T> Eq for ManuallyDrop<T>
where
T: Eq + ?Sized,impl<T> Eq for Saturating<T>
where
T: Eq,impl<T> Eq for Wrapping<T>
where
T: Eq,impl<T> Eq for NonNull<T>
where
T: ?Sized,impl<T> Eq for Reverse<T>
where
T: Eq,impl<T, A> Eq for Box<T, A>
where
T: Eq + ?Sized,
A: Allocator,impl<T, A> Eq for BTreeSet<T, A>
where
T: Eq,
A: Allocator + Clone,impl<T, A> Eq for LinkedList<T, A>
where
T: Eq,
A: Allocator,impl<T, A> Eq for VecDeque<T, A>
where
T: Eq,
A: Allocator,impl<T, A> Eq for Rc<T, A>
where
T: Eq + ?Sized,
A: Allocator,impl<T, A> Eq for Arc<T, A>
where
T: Eq + ?Sized,
A: Allocator,impl<T, A> Eq for Vec<T, A>
where
T: Eq,
A: Allocator,impl<T, E> Eq for Result<T, E>
where
T: Eq,
E: Eq,impl<T, S> Eq for HashSet<T, S>
where
T: Eq + Hash,
S: BuildHasher,impl<T, const N: usize> Eq for [T; N]
where
T: Eq,impl<T, const N: usize> Eq for Simd<T, N>
where
LaneCount<N>: SupportedLaneCount,
T: SimdElement + Eq,impl<T: Eq> Eq for TrySendError<T>impl<T: Eq> Eq for Cursor<T>impl<T: Eq> Eq for SendError<T>impl<T: Eq> Eq for OnceLock<T>impl<Y, R> Eq for CoroutineState<Y, R>
where
Y: Eq,
R: Eq,© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/cmp/trait.Eq.html