user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Clear up discriminants with more examples

Browse source
This commit is contained in:
Ariel Davis 2022-01-15 20:24:38 -08:00
parent 8f33b4eed1
commit 828febf9e0
1 changed files with 52 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

70
library/core/src/cmp.rs
View file

@ -661,20 +661,37 @@ impl<T: Clone> Clone for Reverse<T> {
///
/// ## Derivable
///
/// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a
/// [lexicographic](https://en.wikipedia.org/wiki/Lexicographic_order) ordering based on the top-to-bottom declaration order of the struct's members.
/// When `derive`d on enums, variants are ordered by their top-to-bottom discriminant order.
/// This means variants at the top are less than variants at the bottom.
/// Here's an example:
/// This trait can be used with `#[derive]`.
///
/// When `derive`d on structs, it will produce a
/// [lexicographic](https://en.wikipedia.org/wiki/Lexicographic_order) ordering
/// based on the top-to-bottom declaration order of the struct's members.
///
/// When `derive`d on enums, variants are ordered by their discriminants.
/// By default, the discriminant is smallest for variants at the top, and
/// largest for variants at the bottom. Here's an example:
///
/// ```
/// #[derive(PartialEq, Eq, PartialOrd, Ord)]
/// enum Size {
/// Small,
/// Large,
/// enum E {
/// Top,
/// Bottom,
/// }
///
/// assert!(Size::Small < Size::Large);
/// assert!(E::Top < E::Bottom);
/// ```
///
/// However, manually setting the discriminants can override this default
/// behavior:
////
/// ```
/// #[derive(PartialEq, Eq, PartialOrd, Ord)]
/// enum E {
/// Top = 2,
/// Bottom = 1,
/// }
///
/// assert!(E::Bottom < E::Top);
/// ```
///
/// ## Lexicographical comparison
@ -895,20 +912,37 @@ impl PartialOrd for Ordering {
///
/// ## Derivable
///
/// This trait can be used with `#[derive]`. When `derive`d on structs, it will produce a
/// lexicographic ordering based on the top-to-bottom declaration order of the struct's members.
/// When `derive`d on enums, variants are ordered by their top-to-bottom discriminant order.
/// This means variants at the top are less than variants at the bottom.
/// Here's an example:
/// This trait can be used with `#[derive]`.
///
/// When `derive`d on structs, it will produce a
/// [lexicographic](https://en.wikipedia.org/wiki/Lexicographic_order) ordering
/// based on the top-to-bottom declaration order of the struct's members.
///
/// When `derive`d on enums, variants are ordered by their discriminants.
/// By default, the discriminant is smallest for variants at the top, and
/// largest for variants at the bottom. Here's an example:
///
/// ```
/// #[derive(PartialEq, PartialOrd)]
/// enum Size {
/// Small,
/// Large,
/// enum E {
/// Top,
/// Bottom,
/// }
///
/// assert!(Size::Small < Size::Large);
/// assert!(E::Top < E::Bottom);
/// ```
///
/// However, manually setting the discriminants can override this default
/// behavior:
////
/// ```
/// #[derive(PartialEq, PartialOrd)]
/// enum E {
/// Top = 2,
/// Bottom = 1,
/// }
///
/// assert!(E::Bottom < E::Top);
/// ```
///
/// ## How can I implement `PartialOrd`?