Trait std::cmp::Eq

pub trait Eq: PartialEq<Self> { }

Trait for equality comparisons which are equivalence relations.

This means, that in addition to a == b and a != b being strict inverses, the equality must be (for all a, b and c):

• reflexive: a == a;
• symmetric: a == b implies b == a; and
• transitive: a == b and b == c implies a == c.

This property cannot be checked by the compiler, and therefore Eq implies PartialEq, and has no extra methods.

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: &Book) -> bool {
        self.isbn == other.isbn
    }
}
impl Eq for Book {}

Implementations on Foreign Types

impl<T> Eq for NonZero<T> where
    T: Zeroable + Eq, 

impl Eq for InvalidSequence

impl<'a> Eq for Utf8LossyChunk<'a>

Implementors

• impl<Ret, A, B, C, D, E> Eq for extern "C" fn(A, B, C, D, E) -> Ret
• impl Eq for i8
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for unsafe fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, ...) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
• impl Eq for i16
• impl<A, B, C> Eq for (A, B, C) where
    A: Eq,
    B: Eq,
    C: Eq + ?Sized, 
• impl Eq for CharTryFromError
• impl Eq for u8
• impl<Ret, A, B, C, D, E, F, G, H> Eq for extern "C" fn(A, B, C, D, E, F, G, H) -> Ret
• impl<T> Eq for [T; 8] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
• impl Eq for Duration
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, ...) -> Ret
• impl<Ret, A, B> Eq for unsafe fn(A, B) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
• impl<Ret> Eq for unsafe fn() -> Ret
• impl<A, B, C, D, E, F, G, H, I> Eq for (A, B, C, D, E, F, G, H, I) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq,
    H: Eq,
    I: Eq + ?Sized, 
• impl Eq for ParseFloatError
• impl<Ret, A, B, C, D, E, F, G> Eq for extern "C" fn(A, B, C, D, E, F, G) -> Ret
• impl<T> Eq for [T; 30] where
    T: Eq, 
• impl Eq for u16
• impl Eq for Error
• impl<A, B, C, D> Eq for (A, B, C, D) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq + ?Sized, 
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret
• impl<Ret, A, B, C> Eq for unsafe fn(A, B, C) -> Ret
• impl Eq for NoneError
• impl<T> Eq for [T; 32] where
    T: Eq, 
• impl<T> Eq for Discriminant<T>
• impl<T> Eq for [T; 19] where
    T: Eq, 
• impl<Idx> Eq for RangeToInclusive<Idx> where
    Idx: Eq, 
• impl<A, B> Eq for (A, B) where
    A: Eq,
    B: Eq + ?Sized, 
• impl Eq for FpCategory
• impl<T> Eq for *mut T where
    T: ?Sized, 
• impl<T> Eq for [T; 3] where
    T: Eq, 
• impl<T, E> Eq for Result<T, E> where
    E: Eq,
    T: Eq, 
• impl<T> Eq for [T; 25] where
    T: Eq, 
• impl Eq for ()
• impl<Ret, A, B, C, D> Eq for extern "C" fn(A, B, C, D) -> Ret
• impl<Ret, A, B, C, D, E, F, G> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G) -> Ret
• impl<Ret> Eq for extern "C" fn() -> Ret
• impl<Ret> Eq for fn() -> Ret
• impl<Ret, A, B, C, D, E> Eq for unsafe extern "C" fn(A, B, C, D, E, ...) -> Ret
• impl<Ret, A, B, C> Eq for extern "C" fn(A, B, C, ...) -> Ret
• impl Eq for i32
• impl<T> Eq for [T; 27] where
    T: Eq, 
• impl<T> Eq for NonNull<T> where
    T: ?Sized, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
• impl<T> Eq for RefCell<T> where
    T: Eq + ?Sized, 
• impl<T> Eq for [T; 4] where
    T: Eq, 
• impl Eq for u32
• impl<T> Eq for Option<T> where
    T: Eq, 
• impl<Ret, A> Eq for extern "C" fn(A, ...) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H> Eq for unsafe fn(A, B, C, D, E, F, G, H) -> Ret
• impl<Ret, A> Eq for fn(A) -> Ret
• impl<T> Eq for [T; 2] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H> Eq for fn(A, B, C, D, E, F, G, H) -> Ret
• impl<T> Eq for [T; 15] where
    T: Eq, 
• impl<T> Eq for [T; 16] where
    T: Eq, 
• impl<T> Eq for [T; 14] where
    T: Eq, 
• impl<Ret, A> Eq for unsafe extern "C" fn(A) -> Ret
• impl<Ret> Eq for unsafe extern "C" fn() -> Ret
• impl<Ret, A> Eq for unsafe fn(A) -> Ret
• impl<Ret, A, B, C, D> Eq for extern "C" fn(A, B, C, D, ...) -> Ret
• impl<T> Eq for [T; 0] where
    T: Eq, 
• impl Eq for ParseIntError
• impl<T> Eq for [T; 24] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J, ...) -> Ret
• impl Eq for usize
• impl<A, B, C, D, E, F> Eq for (A, B, C, D, E, F) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq + ?Sized, 
• impl<T> Eq for *const T where
    T: ?Sized, 
• impl<Ret, A> Eq for extern "C" fn(A) -> Ret
• impl<A, B, C, D, E, F, G, H, I, J, K> Eq for (A, B, C, D, E, F, G, H, I, J, K) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq,
    H: Eq,
    I: Eq,
    J: Eq,
    K: Eq + ?Sized, 
• impl<Ret, A, B, C, D, E, F, G, H> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H) -> Ret
• impl<T> Eq for [T; 31] where
    T: Eq, 
• impl<T> Eq for [T; 10] where
    T: Eq, 
• impl<T> Eq for ManuallyDrop<T> where
    T: Eq, 
• impl<T> Eq for [T; 26] where
    T: Eq, 
• impl<Ret, A, B, C> Eq for unsafe extern "C" fn(A, B, C) -> Ret
• impl<T> Eq for [T; 7] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I) -> Ret
• impl<Ret, A, B, C, D> Eq for unsafe fn(A, B, C, D) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L, ...) -> Ret
• impl<Ret, A, B> Eq for fn(A, B) -> Ret
• impl<A, B, C, D, E, F, G> Eq for (A, B, C, D, E, F, G) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq + ?Sized, 
• impl<Idx> Eq for Range<Idx> where
    Idx: Eq, 
• impl<Ret, A, B, C, D, E, F, G> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, ...) -> Ret
• impl<Ret, A, B, C, D, E, F> Eq for unsafe extern "C" fn(A, B, C, D, E, F) -> Ret
• impl Eq for Utf8Error
• impl Eq for SearchStep
• impl<Ret, A, B> Eq for extern "C" fn(A, B, ...) -> Ret
• impl<T> Eq for [T; 29] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for fn(A, B, C, D, E, F, G, H, I) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, ...) -> Ret
• impl<T> Eq for [T; 12] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, ...) -> Ret
• impl<A, B, C, D, E, F, G, H, I, J, K, L> Eq for (A, B, C, D, E, F, G, H, I, J, K, L) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq,
    H: Eq,
    I: Eq,
    J: Eq,
    K: Eq,
    L: Eq + ?Sized, 
• impl<T> Eq for [T; 6] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F> Eq for unsafe fn(A, B, C, D, E, F) -> Ret
• impl<T> Eq for [T; 28] where
    T: Eq, 
• impl<Idx> Eq for RangeFrom<Idx> where
    Idx: Eq, 
• impl<Idx> Eq for RangeTo<Idx> where
    Idx: Eq, 
• impl<Idx> Eq for RangeInclusive<Idx> where
    Idx: Eq, 
• impl Eq for Ordering
• impl Eq for Infallible
• impl<Ret, A, B, C> Eq for fn(A, B, C) -> Ret
• impl<Ret, A, B, C, D, E, F> Eq for extern "C" fn(A, B, C, D, E, F) -> Ret
• impl<A, B, C, D, E, F, G, H> Eq for (A, B, C, D, E, F, G, H) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq,
    H: Eq + ?Sized, 
• impl<A, B, C, D, E> Eq for (A, B, C, D, E) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq + ?Sized, 
• impl Eq for i128
• impl<Ret, A, B> Eq for extern "C" fn(A, B) -> Ret
• impl Eq for i64
• impl<T> Eq for [T; 5] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K) -> Ret
• impl<Ret, A, B, C, D, E, F, G> Eq for extern "C" fn(A, B, C, D, E, F, G, ...) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, ...) -> Ret
• impl Eq for u64
• impl Eq for bool
• impl<Ret, A, B, C, D> Eq for unsafe extern "C" fn(A, B, C, D, ...) -> Ret
• impl<Y, R> Eq for GeneratorState<Y, R> where
    R: Eq,
    Y: Eq, 
• impl<Ret, A, B, C> Eq for unsafe extern "C" fn(A, B, C, ...) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret
• impl<T> Eq for Reverse<T> where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H> Eq for extern "C" fn(A, B, C, D, E, F, G, H, ...) -> Ret
• impl<T> Eq for [T; 18] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F> Eq for unsafe extern "C" fn(A, B, C, D, E, F, ...) -> Ret
• impl Eq for isize
• impl<Ret, A, B, C> Eq for extern "C" fn(A, B, C) -> Ret
• impl<Ret, A> Eq for unsafe extern "C" fn(A, ...) -> Ret
• impl<T> Eq for PhantomData<T> where
    T: ?Sized, 
• impl Eq for ParseBoolError
• impl<T> Eq for [T] where
    T: Eq, 
• impl Eq for ParseCharError
• impl<T> Eq for [T; 13] where
    T: Eq, 
• impl Eq for RangeFull
• impl<T> Eq for Wrapping<T> where
    T: Eq, 
• impl<T> Eq for [T; 17] where
    T: Eq, 
• impl Eq for !
• impl<T> Eq for [T; 23] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G> Eq for unsafe fn(A, B, C, D, E, F, G) -> Ret
• impl<Ret, A, B> Eq for unsafe extern "C" fn(A, B) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for unsafe fn(A, B, C, D, E, F, G, H, I, J) -> Ret
• impl<A> Eq for (A,) where
    A: Eq + ?Sized, 
• impl<T> Eq for Cell<T> where
    T: Copy + Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L, ...) -> Ret
• impl<'a, A> Eq for &'a A where
    A: Eq + ?Sized, 
• impl<T> Eq for [T; 21] where
    T: Eq, 
• impl<A, B, C, D, E, F, G, H, I, J> Eq for (A, B, C, D, E, F, G, H, I, J) where
    A: Eq,
    B: Eq,
    C: Eq,
    D: Eq,
    E: Eq,
    F: Eq,
    G: Eq,
    H: Eq,
    I: Eq,
    J: Eq + ?Sized, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for fn(A, B, C, D, E, F, G, H, I, J) -> Ret
• impl<T> Eq for [T; 1] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G> Eq for fn(A, B, C, D, E, F, G) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for unsafe extern "C" fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
• impl<Ret, A, B, C, D, E> Eq for fn(A, B, C, D, E) -> Ret
• impl<T> Eq for [T; 9] where
    T: Eq, 
• impl Eq for char
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, ...) -> Ret
• impl Eq for u128
• impl<Ret, A, B, C, D, E, F> Eq for extern "C" fn(A, B, C, D, E, F, ...) -> Ret
• impl<Ret, A, B> Eq for unsafe extern "C" fn(A, B, ...) -> Ret
• impl<Ret, A, B, C, D> Eq for fn(A, B, C, D) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I> Eq for unsafe fn(A, B, C, D, E, F, G, H, I) -> Ret
• impl Eq for TypeId
• impl<Ret, A, B, C, D, E, F> Eq for fn(A, B, C, D, E, F) -> Ret
• impl<'a, A> Eq for &'a mut A where
    A: Eq + ?Sized, 
• impl<Ret, A, B, C, D, E> Eq for unsafe extern "C" fn(A, B, C, D, E) -> Ret
• impl<Ret, A, B, C, D, E> Eq for extern "C" fn(A, B, C, D, E, ...) -> Ret
• impl<Ret, A, B, C, D, E> Eq for unsafe fn(A, B, C, D, E) -> Ret
• impl<T> Eq for [T; 11] where
    T: Eq, 
• impl<Ret, A, B, C, D, E, F, G, H, I, J, K, L> Eq for unsafe fn(A, B, C, D, E, F, G, H, I, J, K, L) -> Ret
• impl<Ret, A, B, C, D, E, F, G, H, I, J> Eq for extern "C" fn(A, B, C, D, E, F, G, H, I, J) -> Ret
• impl<Ret, A, B, C, D> Eq for unsafe extern "C" fn(A, B, C, D) -> Ret
• impl<T> Eq for [T; 20] where
    T: Eq, 
• impl<T> Eq for [T; 22] where
    T: Eq, 
• impl Eq for str
• impl Eq for AllocErr
• impl Eq for String
• impl Eq for Layout
• impl<T> Eq for Box<T> where
    T: Eq + ?Sized, 
• impl<T> Eq for Arc<T> where
    T: Eq + ?Sized, 
• impl<T> Eq for BTreeSet<T> where
    T: Eq, 
• impl<A> Eq for VecDeque<A> where
    A: Eq, 
• impl<T> Eq for Rc<T> where
    T: Eq + ?Sized, 
• impl<T> Eq for LinkedList<T> where
    T: Eq, 
• impl Eq for CannotReallocInPlace
• impl<T> Eq for Vec<T> where
    T: Eq, 
• impl<'a, B> Eq for Cow<'a, B> where
    B: Eq + ToOwned + ?Sized, 
• impl<T> Eq for Bound<T> where
    T: Eq, 
• impl Eq for ParseError
• impl<K, V> Eq for BTreeMap<K, V> where
    K: Eq,
    V: Eq, 
• impl Eq for DecodeUtf16Error
• impl Eq for UnicodeVersion
• impl Eq for LocalKeyState
• impl Eq for ThreadId
• impl<K, V, S> Eq for HashMap<K, V, S> where
    K: Eq + Hash,
    V: Eq,
    S: BuildHasher, 
• impl<T, S> Eq for HashSet<T, S> where
    T: Eq + Hash,
    S: BuildHasher, 
• impl Eq for VarError
• impl Eq for CString
• impl Eq for NulError
• impl Eq for FromBytesWithNulError
• impl Eq for IntoStringError
• impl Eq for CStr
• impl Eq for OsString
• impl Eq for OsStr
• impl Eq for Permissions
• impl Eq for FileType
• impl Eq for ErrorKind
• impl Eq for SeekFrom
• impl Eq for IpAddr
• impl Eq for Ipv6MulticastScope
• impl Eq for Ipv4Addr
• impl Eq for Ipv6Addr
• impl Eq for SocketAddr
• impl Eq for SocketAddrV4
• impl Eq for SocketAddrV6
• impl Eq for AddrParseError
• impl Eq for Shutdown
• impl<'a> Eq for Prefix<'a>
• impl<'a> Eq for PrefixComponent<'a>
• impl<'a> Eq for Component<'a>
• impl<'a> Eq for Components<'a>
• impl Eq for PathBuf
• impl Eq for StripPrefixError
• impl Eq for Path
• impl Eq for Output
• impl Eq for ExitStatus
• impl<T: Eq> Eq for SendError<T>
• impl Eq for RecvError
• impl Eq for TryRecvError
• impl Eq for RecvTimeoutError
• impl<T: Eq> Eq for TrySendError<T>
• impl Eq for WaitTimeoutResult
• impl Eq for Instant
• impl Eq for SystemTime