Trait concordium_std::cmp::Eq

1.0.0 · source ·

pub trait Eq: PartialEq { }

Expand description

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 == b implies b == a (required by PartialEq as well); and
transitive: a == b and b == c implies a == c (required by PartialEq as 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.

Trait concordium_std::cmp::Eq

§Derivable

§How can I implement Eq?

Object Safety§

Implementors§

impl Eq for TryReserveErrorKind

impl Eq for Infallible

impl Eq for AccountKind

impl Eq for Address

impl Eq for AmountParseError

impl Eq for CheckAccountSignatureError

impl Eq for LogError

impl Eq for NewAttributeValueError

impl Eq for NewContractNameError

impl Eq for NewReceiveNameError

impl Eq for ParseDurationError

impl Eq for PublicKey

impl Eq for Signature

impl Eq for SignatureKind

impl Eq for TransferError

impl Eq for UpgradeError

impl Eq for WasmVersion

impl Eq for concordium_std::fmt::Alignment

impl Eq for PureHashMarker

impl Eq for FpCategory

impl Eq for IntErrorKind

impl Eq for Fields

impl Eq for FunctionV1

impl Eq for SizeLength

impl Eq for Type

impl Eq for TestStateError

impl Eq for concordium_std::cmp::Ordering

impl Eq for AsciiChar

impl Eq for IpAddr

impl Eq for Ipv6MulticastScope

impl Eq for SocketAddr

impl Eq for SearchStep

impl Eq for core::sync::atomic::Ordering

impl Eq for BacktraceStatus

impl Eq for VarError

impl Eq for SeekFrom

impl Eq for ErrorKind

impl Eq for Shutdown

impl Eq for BacktraceStyle

impl Eq for RecvTimeoutError

impl Eq for TryRecvError

impl Eq for hashbrown::TryReserveError

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 ()

impl Eq for usize

impl Eq for UnorderedKeyError

impl Eq for concordium_std::collections::TryReserveError

impl Eq for Error

impl Eq for PhantomPinned

impl Eq for Assume

impl Eq for ParseFloatError

impl Eq for ParseIntError

impl Eq for TryFromIntError

impl Eq for RangeFull

impl Eq for ContractV0

impl Eq for ContractV1

impl Eq for ContractV2

impl Eq for ContractV3

impl Eq for FunctionV2

impl Eq for ModuleV0

impl Eq for ModuleV1

§How can I implement `Eq`?