22 lines
7.4 KiB
Plaintext
22 lines
7.4 KiB
Plaintext
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rust
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< #rustc 1.96.0 (ac68faa20 2026-05-25)ÁíàÄTËŸ ÜJîÄ)'ß\¥! -3d1337db07d0b3aeÁ ¤°ð ¾ä-±($²ï=©Ã -7e98a21bfd32b0edÁ‰ í
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EquivalentÁ œ
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equivalentÁ ¢ œ º
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ComparableÁ œ compareÁ ¢ œ ü
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¢œ ÅË í Y4Ü ®Dó ¿ß ü Ë ü L I [`Equivalent`] and [`Comparable`] are traits for key comparison in maps.Á M ú 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 ú 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  ú 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 ú t± # ExamplesÁ À ú <Ä ```Á ´Ì use equivalent::*;Á Üã use std::cmp::Ordering;Á ÿ ú üƒ( % pub struct Pair<A, B>(pub A, pub B);Á ¬ ú 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 ú üÓR O impl<'a, A: ?Sized, B: ?Sized, C, D> Comparable<(C, D)> for Pair<&'a A, &'a B>Á L¦ ö Ì° A: Comparable<C>,Á ÌÊ B: Comparable<D>,Á ,ä Ì 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 ä
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,Æ ö
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Ì ú |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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ú 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 … ú 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 ,¯ ö
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