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Edit docs on consistency of PartialOrd and PartialEq #94620

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Mar 5, 2022
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Edit docs on consistency of PartialOrd and PartialEq #94620

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25 changes: 12 additions & 13 deletions library/core/src/cmp.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -885,19 +885,18 @@ impl PartialOrd for Ordering {
/// The `lt`, `le`, `gt`, and `ge` methods of this trait can be called using
/// the `<`, `<=`, `>`, and `>=` operators, respectively.
///
/// The methods of this trait must be consistent with each other and with those of `PartialEq` in
/// the following sense:
///
/// - `a == b` if and only if `partial_cmp(a, b) == Some(Equal)`.
/// - `a < b` if and only if `partial_cmp(a, b) == Some(Less)`
/// (ensured by the default implementation).
/// - `a > b` if and only if `partial_cmp(a, b) == Some(Greater)`
/// (ensured by the default implementation).
/// - `a <= b` if and only if `a < b || a == b`
/// (ensured by the default implementation).
/// - `a >= b` if and only if `a > b || a == b`
/// (ensured by the default implementation).
/// - `a != b` if and only if `!(a == b)` (already part of `PartialEq`).
/// The methods of this trait must be consistent with each other and with those of [`PartialEq`].
/// The following conditions must hold:
///
/// 1. `a == b` if and only if `partial_cmp(a, b) == Some(Equal)`.
/// 2. `a < b` if and only if `partial_cmp(a, b) == Some(Less)`
/// 3. `a > b` if and only if `partial_cmp(a, b) == Some(Greater)`
/// 4. `a <= b` if and only if `a < b || a == b`
/// 5. `a >= b` if and only if `a > b || a == b`
/// 6. `a != b` if and only if `!(a == b)`.
///
/// Conditions 2–5 above are ensured by the default implementation.
/// Condition 6 is already ensured by [`PartialEq`].
///
/// If [`Ord`] is also implemented for `Self` and `Rhs`, it must also be consistent with
/// `partial_cmp` (see the documentation of that trait for the exact requirements). It's
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