Trait Eq

1.0.0 (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 DispatchClass

impl Eq for Pays

impl Eq for Never

impl Eq for FailedMigrationHandling

impl Eq for SteppedMigrationError

impl Eq for topsoil_core::pallet_prelude::DispatchError

impl Eq for InvalidTransaction

impl Eq for TransactionSource

impl Eq for TransactionValidityError

impl Eq for UnknownTransaction

impl Eq for ChildInfo

impl Eq for DecRefStatus

impl Eq for IncRefStatus

impl Eq for topsoil_core::system::Phase

impl Eq for ExecuteOverweightError

impl Eq for ProcessMessageError

impl Eq for topsoil_core::traits::TrieError

impl Eq for Judgement

impl Eq for Statement

impl Eq for Truth

impl Eq for Social

impl Eq for LookupError

impl Eq for BalanceStatus

impl Eq for DepositConsequence

impl Eq for ExistenceRequirement

impl Eq for Fortitude

impl Eq for Precision

impl Eq for Preservation

impl Eq for Provenance

impl Eq for Restriction

impl Eq for TransferStatus

impl Eq for topsoil_core::runtime::app_crypto::core_::bounded::alloc::collections::TryReserveErrorKind

impl Eq for topsoil_core::runtime::app_crypto::core_::crypto::AddressUriError

impl Eq for PublicError

impl Eq for Ss58AddressFormatRegistry

impl Eq for Void

impl Eq for CallContext

impl Eq for DeriveError

impl Eq for DeriveJunction

impl Eq for SecretStringError

impl Eq for ArithmeticError

impl Eq for DigestItem

impl Eq for ExtrinsicInclusionMode

impl Eq for MultiSignature

impl Eq for MultiSigner

impl Eq for StateVersion

impl Eq for TokenError

impl Eq for TransactionalError

impl Eq for Era

impl Eq for topsoil_core::runtime::legacy::byte_sized_error::DispatchError

impl Eq for HttpError

impl Eq for HttpRequestStatus

impl Eq for OffchainOverlayedChange

impl Eq for StorageKind

impl Eq for topsoil_core::runtime::offchain::http::Error

impl Eq for Method

impl Eq for StorageRetrievalError

impl Eq for PathError

impl Eq for TypeDefPrimitive

impl Eq for MetaForm

impl Eq for PortableForm

impl Eq for Infallible

impl Eq for topsoil_core::runtime::std::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for Sign

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for topsoil_core::runtime::std::slice::GetDisjointMutError

impl Eq for SearchStep

impl Eq for topsoil_core::runtime::std::sync::atomic::Ordering

impl Eq for RecvTimeoutError

impl Eq for topsoil_core::runtime::std::sync::mpmc::TryRecvError

impl Eq for topsoil_core::runtime::std::cmp::Ordering

impl Eq for AsciiChar

Trait Eq

§How can I implement `Eq`?