Trait void::coreprovider::cmp::PartialEq1.0.0[][src]

#[lang = "eq"]
pub trait PartialEq<Rhs = Self> where
    Rhs: ?Sized
{
#[must_use]
fn eq(&self, other: &Rhs) -> bool;
#[must_use]
fn ne(&self, other: &Rhs) -> bool { ... } }

Trait for equality comparisons which are partial equivalence relations.

This trait allows for partial equality, for types that do not have a full equivalence relation. For example, in floating point numbers NaN != NaN, so floating point types implement PartialEq but not Eq.

Formally, the equality must be (for all a, b and c):

Note that these requirements mean that the trait itself must be implemented symmetrically and transitively: if T: PartialEq<U> and U: PartialEq<V> then U: PartialEq<T> and T: PartialEq<V>.

Derivable

This trait can be used with #[derive]. When derived on structs, two instances are equal if all fields are equal, and not equal if any fields are not equal. When derived on enums, each variant is equal to itself and not equal to the other variants.

How can I implement PartialEq?

PartialEq only requires the eq method to be implemented; ne is defined in terms of it by default. Any manual implementation of ne must respect the rule that eq is a strict inverse of ne; that is, !(a == b) if and only if a != b.

Implementations of PartialEq, PartialOrd, and Ord must agree with each other. It's easy to accidentally make them disagree by deriving some of the traits and manually implementing others.

An example implementation for a domain in which two books are considered the same book if their ISBN matches, even if the formats differ:

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
    }
}

let b1 = Book { isbn: 3, format: BookFormat::Paperback };
let b2 = Book { isbn: 3, format: BookFormat::Ebook };
let b3 = Book { isbn: 10, format: BookFormat::Paperback };

assert!(b1 == b2);
assert!(b1 != b3);

Examples

let x: u32 = 0;
let y: u32 = 1;

assert_eq!(x == y, false);
assert_eq!(x.eq(&y), false);

Required Methods

This method tests for self and other values to be equal, and is used by ==.

Provided Methods

This method tests for !=.

Implementations on Foreign Types

impl PartialEq<DecodeUtf16Error> for DecodeUtf16Error
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impl PartialEq<CharTryFromError> for CharTryFromError
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impl<H> PartialEq<BuildHasherDefault<H>> for BuildHasherDefault<H>
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impl<T> PartialEq<Wrapping<T>> for Wrapping<T> where
    T: PartialEq<T>, 
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impl PartialEq<NonZeroUsize> for NonZeroUsize
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impl<'a> PartialEq<Utf8LossyChunk<'a>> for Utf8LossyChunk<'a>
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impl PartialEq<NoneError> for NoneError
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impl<T> PartialEq<ManuallyDrop<T>> for ManuallyDrop<T> where
    T: PartialEq<T>, 
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impl PartialEq<FpCategory> for FpCategory
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impl PartialEq<Utf8Error> for Utf8Error
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impl<Idx> PartialEq<Range<Idx>> for Range<Idx> where
    Idx: PartialEq<Idx>, 
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impl PartialEq<NonZeroU32> for NonZeroU32
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impl<Idx> PartialEq<RangeFrom<Idx>> for RangeFrom<Idx> where
    Idx: PartialEq<Idx>, 
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impl<T> PartialEq<Discriminant<T>> for Discriminant<T>
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impl<T> PartialEq<Bound<T>> for Bound<T> where
    T: PartialEq<T>, 
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impl<T> PartialEq<PhantomData<T>> for PhantomData<T> where
    T: ?Sized
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impl PartialEq<TypeId> for TypeId
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impl<T> PartialEq<NonNull<T>> for NonNull<T> where
    T: ?Sized
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impl PartialEq<LayoutErr> for LayoutErr
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impl<Idx> PartialEq<RangeToInclusive<Idx>> for RangeToInclusive<Idx> where
    Idx: PartialEq<Idx>, 
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impl PartialEq<Layout> for Layout
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impl PartialEq<NonZeroU16> for NonZeroU16
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impl PartialEq<NonZeroU128> for NonZeroU128
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impl<Idx> PartialEq<RangeTo<Idx>> for RangeTo<Idx> where
    Idx: PartialEq<Idx>, 
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impl<T> PartialEq<Poll<T>> for Poll<T> where
    T: PartialEq<T>, 
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impl PartialEq<AllocErr> for AllocErr
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impl PartialEq<InvalidSequence> for InvalidSequence
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impl<T> PartialEq<Option<T>> for Option<T> where
    T: PartialEq<T>, 
[src]

impl PartialEq<ParseFloatError> for ParseFloatError
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impl<T, E> PartialEq<Result<T, E>> for Result<T, E> where
    E: PartialEq<E>,
    T: PartialEq<T>, 
[src]

impl<T> PartialEq<RefCell<T>> for RefCell<T> where
    T: PartialEq<T> + ?Sized
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Panics

Panics if the value in either RefCell is currently borrowed.

impl PartialEq<ParseIntError> for ParseIntError
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impl<T> PartialEq<Cell<T>> for Cell<T> where
    T: Copy + PartialEq<T>, 
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impl PartialEq<Pinned> for Pinned
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impl PartialEq<NonZeroU8> for NonZeroU8
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impl PartialEq<ParseBoolError> for ParseBoolError
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impl PartialEq<ParseCharError> for ParseCharError
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impl PartialEq<Duration> for Duration
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impl<Idx> PartialEq<RangeInclusive<Idx>> for RangeInclusive<Idx> where
    Idx: PartialEq<Idx>, 
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impl PartialEq<CannotReallocInPlace> for CannotReallocInPlace
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impl<Y, R> PartialEq<GeneratorState<Y, R>> for GeneratorState<Y, R> where
    R: PartialEq<R>,
    Y: PartialEq<Y>, 
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impl PartialEq<RangeFull> for RangeFull
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impl PartialEq<SearchStep> for SearchStep
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impl PartialEq<NonZeroU64> for NonZeroU64
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impl PartialEq<UnicodeVersion> for UnicodeVersion
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Implementors