24 lines
7.2 KiB
Plaintext
24 lines
7.2 KiB
Plaintext
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rust
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C #rustc 1.93.0 (254b59607 2026-01-19)Á³VOÐêùÿ²?ÑL¼�§Ì± -a7a40eb546f9e2b0Á ë&Gf·Ã ¬ëñq:¤»b -bb76018b1173caf6Á‰ ³
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EquivalentÁ KÁ
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equivalentÁ QÁ ³ »
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ComparableÁ ³ compareÁ Ð ³ þ
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г ÇÍ ³ g4Ü ¦ ÕDó üÕ ü Ë ü L I [`Equivalent`] and [`Comparable`] are traits for key comparison in maps.Á M Ë üQM J These may be used in the implementation of maps where the lookup type `Q`Á üŸ2 / may be different than the stored key type `K`.Á Ò Ë üÖL I * `Q: Equivalent<K>` checks for equality, similar to the `HashMap<K, V>`Á ü£' $ constraint `K: Borrow<Q>, Q: Eq`.Á üËM J * `Q: Comparable<K>` checks the ordering, similar to the `BTreeMap<K, V>`Á ü™( % constraint `K: Borrow<Q>, Q: Ord`.Á Â Ë üÆO L These traits are not used by the maps in the standard library, but they mayÁ ü–J G add more flexibility in third-party map implementations, especially inÁ üáK H situations where a strict `K: Borrow<Q>` relationship is not available.Á Ë t± # ExamplesÁ À Ë <Ä ```Á ´Ì use equivalent::*;Á Üã use std::cmp::Ordering;Á ÿ Ë üƒ( % pub struct Pair<A, B>(pub A, pub B);Á ¬ Ë ü°R O impl<'a, A: ?Sized, B: ?Sized, C, D> Equivalent<(C, D)> for Pair<&'a A, &'a B>Á Lƒ whereÁ Ì� A: Equivalent<C>,Á ̧ B: Equivalent<D>,Á ,Á {Á üÇ4 1 fn equivalent(&self, key: &(C, D)) -> bool {Á üüB ? self.0.equivalent(&key.0) && self.1.equivalent(&key.1)Á L¿ }Á ,É }Á Ï Ë üÓR O impl<'a, A: ?Sized, B: ?Sized, C, D> Comparable<(C, D)> for Pair<&'a A, &'a B>Á L¦ ß Ì° A: Comparable<C>,Á ÌÊ B: Comparable<D>,Á ,ä ² üê 5 2 fn compare(&self, key: &(C, D)) -> Ordering {Á ü
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* ' match self.0.compare(&key.0) {Á üË
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: 7 Ordering::Equal => self.1.compare(&key.1),Á ü† ' $ not_equal => not_equal,Á l®
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}Á L¼ Ç
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,Æ Ø
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Ì Ë |Ð fn main() {Á üà = : let key = (String::from("foo"), String::from("bar"));Á üž $ ! let q1 = Pair("foo", "bar");Á üà $ ! let q2 = Pair("boo", "bar");Á üè $ ! let q3 = Pair("foo", "baz");Á �
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Ë ü‘
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% " assert!(q1.equivalent(&key));Á ü·
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& # assert!(!q2.equivalent(&key));Á üÞ
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& # assert!(!q3.equivalent(&key));Á … Ë ü‰6 3 assert_eq!(q1.compare(&key), Ordering::Equal);Á üÀ5 2 assert_eq!(q2.compare(&key), Ordering::Less);Á üö8 5 assert_eq!(q3.compare(&key), Ordering::Greater);Á ,¯ Ø
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<µ í ³r g€ ¦ Õ“ üÕ ¤Î €œè “üû Ôþ Key equivalence trait.Á ™ Ë ü�L I This trait allows hash table lookup to be customized. It has one blanketÁ üêN K implementation that uses the regular solution with `Borrow` and `Eq`, justÁ ü¹N K like `HashMap` does, so that you can pass `&str` to lookup into a map withÁ äˆ `String` keys and so on.Á ¥ Ë t© # ContractÁ ¸ Ë ü¼> ; The implementor **must** hash like `K`, if it is hashable.Á T… ³ ªâ üû‘ ªâÍ � Ñ( Ñ- $& üä& ü¡> ; Compare self to `key` and return `true` if they are equal.ÁTç Ù Í ò
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ÙÍ$ó keyÁ ù üŽQ Ð ³
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