Trait Eq

1.0.0 (const: unstable) · Source

pub(crate) 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
transitive: a == b and b == c implies a == c
consistent: a != b if and only if !(a == b)

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 tpacket_versions

impl Eq for libc::prelude::fmt::Alignment

impl Eq for DebugAsHex

impl Eq for Sign

impl Eq for AsciiChar

impl Eq for CharCase

impl Eq for core::cmp::Ordering

impl Eq for Infallible

impl Eq for FromBytesWithNulError

impl Eq for Locality

impl Eq for AtomicOrdering

impl Eq for SimdAlign

impl Eq for ErrorKind

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 core::sync::atomic::Ordering

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 Dl_info

impl Eq for Elf32_Chdr

impl Eq for Elf32_Ehdr

impl Eq for Elf32_Phdr

impl Eq for Elf32_Shdr

impl Eq for Elf32_Sym

impl Eq for Elf64_Chdr

impl Eq for Elf64_Ehdr

impl Eq for Elf64_Phdr

impl Eq for Elf64_Shdr

impl Eq for Elf64_Sym

impl Eq for __c_anonymous__kernel_fsid_t

impl Eq for __c_anonymous_elf32_rel

impl Eq for __c_anonymous_elf32_rela

impl Eq for __c_anonymous_elf64_rel

impl Eq for __c_anonymous_elf64_rela

impl Eq for __c_anonymous_ifru_map

impl Eq for __c_anonymous_ptrace_syscall_info_entry

impl Eq for __c_anonymous_ptrace_syscall_info_exit

impl Eq for __c_anonymous_ptrace_syscall_info_seccomp

impl Eq for __c_anonymous_sockaddr_can_j1939

impl Eq for __c_anonymous_sockaddr_can_tp

impl Eq for __exit_status

impl Eq for __timeval

impl Eq for _libc_fpstate

impl Eq for _libc_fpxreg

impl Eq for _libc_xmmreg

impl Eq for addrinfo

impl Eq for aiocb

impl Eq for arpd_request

impl Eq for arphdr

impl Eq for arpreq

impl Eq for arpreq_old

impl Eq for bcm_msg_head

impl Eq for bcm_timeval

impl Eq for can_berr_counter

Trait Eq

§How can I implement `Eq`?