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Clarify upfront that PartialOrd is for strict partial orders #140779

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Clarify upfront that PartialOrd is for strict partial orders #140779

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Clarify upfront that `PartialOrd` is for strict partial orders
Muon May 8, 2025
7455dbc
Merge branch 'rust-lang:master' into patch-1
Muon May 22, 2025
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9 changes: 5 additions & 4 deletions library/core/src/cmp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,8 @@
//! * [`Eq`] indicates that the overloaded `==` operator corresponds to an
//! equivalence relation.
//! * [`Ord`] and [`PartialOrd`] are traits that allow you to define total and
//! partial orderings between values, respectively. Implementing them overloads
//! the `<`, `<=`, `>`, and `>=` operators.
//! strict partial orderings between values, respectively. Implementing them
//! overloads the `<`, `<=`, `>`, and `>=` operators.
//! * [`Ordering`] is an enum returned by the main functions of [`Ord`] and
//! [`PartialOrd`], and describes an ordering of two values (less, equal, or
//! greater).
Expand Down Expand Up @@ -1095,7 +1095,7 @@ pub macro Ord($item:item) {
/* compiler built-in */
}

/// Trait for types that form a [partial order](https://en.wikipedia.org/wiki/Partial_order).
/// Trait for types that form a [strict partial order](https://en.wikipedia.org/wiki/Strict_partial_order).
///
/// The `lt`, `le`, `gt`, and `ge` methods of this trait can be called using the `<`, `<=`, `>`, and
/// `>=` operators, respectively.
Expand Down Expand Up @@ -1163,7 +1163,8 @@ pub macro Ord($item:item) {
/// The following corollaries follow from the above requirements:
///
/// - irreflexivity of `<` and `>`: `!(a < a)`, `!(a > a)`
/// - transitivity of `>`: if `a > b` and `b > c` then `a > c`
/// - transitivity of `>`: if `a > b` and `b > c`, then `a > c`
/// - antisymmetry of `<=`: if `a <= b` and `b <= a`, then `a == b`
/// - duality of `partial_cmp`: `partial_cmp(a, b) == partial_cmp(b, a).map(Ordering::reverse)`
///
/// ## Strict and non-strict partial orders
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