这些 trait 支持在值之间进行比较。对于包含实现这些 trait 的字段,可以派生所有这些 trait。
PartialEq
指部分等价关系,其中包含必需的方法 eq
和提供的方法 ne
。==
和 !=
运算符会调用这些方法。
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Eq
is a full equivalence relation (reflexive, symmetric, and transitive) and implies PartialEq
. Functions that require full equivalence will use Eq
as a trait bound.
PartialOrd
定义了使用 partial_cmp
方法的部分排序。它用于实现 <
、<=
、>=
和 >
运算符。
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Ord
是总排序,其中 cmp
返回 Ordering
。
Speaker Notes
This slide should take about 10 minutes.
PartialEq
可以在不同类型之间实现,但 Eq
不能,因为它具有自反性:
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在实践中,派生这些 trait 很常见,但很少会实现它们。