Trait Eq

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1.0.0 · Source

pub trait Eq: PartialEq { }

Expand description

core 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.

Trait EqCopy item path

§Derivable

§How can I implement Eq?

Dyn Compatibility§

Implementors§

impl Eq for devela::_core::ascii::Char

impl Eq for FromBytesWithNulError

impl Eq for DebugAsHex

impl Eq for devela::_core::fmt::Sign

impl Eq for Ipv6MulticastScope

impl Eq for GetDisjointMutError

impl Eq for SearchStep

impl Eq for TryReserveErrorKind

impl Eq for devela::_dep::_std::io::SeekFrom

impl Eq for BacktraceStyle

impl Eq for devela::_dep::_std::sync::mpmc::RecvTimeoutError

impl Eq for devela::_dep::_std::sync::mpmc::TryRecvError

impl Eq for CollectionAllocErr

impl Eq for CheckedCastError

impl Eq for PodCastError

impl Eq for devela::_dep::crossterm::event::Event

impl Eq for devela::_dep::crossterm::event::KeyCode

impl Eq for KeyEventKind

impl Eq for MediaKeyCode

impl Eq for ModifierKeyCode

impl Eq for devela::_dep::crossterm::event::MouseButton

impl Eq for MouseEventKind

impl Eq for Attribute

impl Eq for devela::_dep::crossterm::style::Color

impl Eq for Colored

impl Eq for ClearType

impl Eq for ContrastMode

impl Eq for devela::_dep::fltk::app::MouseButton

impl Eq for MouseWheel

impl Eq for devela::_dep::fltk::app::Option

impl Eq for devela::_dep::fltk::app::Scheme

impl Eq for BrowserScrollbar

impl Eq for BrowserType

impl Eq for ButtonType

impl Eq for BeepType

impl Eq for ColorMode

impl Eq for FileDialogType

impl Eq for CallbackReason

impl Eq for ColorDepth

impl Eq for devela::_dep::fltk::enums::Cursor

impl Eq for FrameType

impl Eq for LabelType

impl Eq for FlexType

impl Eq for PackType

impl Eq for ScrollType

impl Eq for TabsOverflow

impl Eq for RgbScaling

impl Eq for InputType

impl Eq for MenuButtonType

impl Eq for WindowMenuStyle

impl Eq for ChartType

impl Eq for ClockType

impl Eq for OutputType

impl Eq for FltkErrorKind

impl Eq for TableContext

impl Eq for TableResizeFlag

impl Eq for TableRowSelectFlag

impl Eq for TableRowSelectMode

impl Eq for XtermColor

impl Eq for devela::_dep::fltk::text::Cursor

impl Eq for DragType

impl Eq for TextAttr

impl Eq for WrapMode

impl Eq for TreeConnectorStyle

impl Eq for TreeItemDrawMode

impl Eq for TreeItemReselectMode

impl Eq for TreeItemSelect

impl Eq for TreeReason

impl Eq for TreeSelect

impl Eq for TreeSort

impl Eq for CounterType

impl Eq for DialType

impl Eq for ScrollbarType

impl Eq for SliderType

impl Eq for WindowType

Trait Eq

§How can I implement `Eq`?