├── .github └── workflows │ └── ci.yml ├── .gitignore ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── README.md └── src └── lib.rs /.github/workflows/ci.yml: -------------------------------------------------------------------------------- 1 | on: 2 | push: 3 | branches: [ main ] 4 | pull_request: 5 | branches: [ main ] 6 | merge_group: 7 | 8 | name: CI 9 | 10 | env: 11 | CARGO_TERM_COLOR: always 12 | CARGO_INCREMENTAL: 0 13 | 14 | jobs: 15 | tests: 16 | runs-on: ubuntu-latest 17 | strategy: 18 | matrix: 19 | include: 20 | - rust: 1.6.0 # MSRV 21 | - rust: stable 22 | - rust: beta 23 | - rust: nightly 24 | 25 | steps: 26 | - uses: actions/checkout@v4 27 | - uses: dtolnay/rust-toolchain@master 28 | with: 29 | toolchain: ${{ matrix.rust }} 30 | - name: Tests 31 | run: | 32 | cargo build --verbose 33 | cargo test --verbose 34 | 35 | # One job that "summarizes" the success state of this pipeline. This can then be added to branch 36 | # protection, rather than having to add each job separately. 37 | success: 38 | name: Success 39 | runs-on: ubuntu-latest 40 | needs: [tests] 41 | # Github branch protection is exceedingly silly and treats "jobs skipped because a dependency 42 | # failed" as success. So we have to do some contortions to ensure the job fails if any of its 43 | # dependencies fails. 44 | if: always() # make sure this is never "skipped" 45 | steps: 46 | # Manually check the status of all dependencies. `if: failure()` does not work. 47 | - name: check if any dependency failed 48 | run: jq --exit-status 'all(.result == "success")' <<< '${{ toJson(needs) }}' 49 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | /Cargo.lock 3 | -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "equivalent" 3 | version = "1.0.2" 4 | rust-version = "1.6" 5 | license = "Apache-2.0 OR MIT" 6 | description = "Traits for key comparison in maps." 7 | repository = "https://github.com/indexmap-rs/equivalent" 8 | keywords = ["hashmap", "no_std"] 9 | categories = ["data-structures", "no-std"] 10 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 21 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 22 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 23 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 24 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 25 | DEALINGS IN THE SOFTWARE. 26 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Equivalent 2 | 3 | [![crates.io](https://img.shields.io/crates/v/equivalent.svg)](https://crates.io/crates/equivalent) 4 | [![docs](https://docs.rs/equivalent/badge.svg)](https://docs.rs/equivalent) 5 | 6 | `Equivalent` and `Comparable` are Rust traits for key comparison in maps. 7 | 8 | These may be used in the implementation of maps where the lookup type `Q` 9 | may be different than the stored key type `K`. 10 | 11 | * `Q: Equivalent` checks for equality, similar to the `HashMap` 12 | constraint `K: Borrow, Q: Eq`. 13 | * `Q: Comparable` checks the ordering, similar to the `BTreeMap` 14 | constraint `K: Borrow, Q: Ord`. 15 | 16 | These traits are not used by the maps in the standard library, but they may 17 | add more flexibility in third-party map implementations, especially in 18 | situations where a strict `K: Borrow` relationship is not available. 19 | 20 | ## License 21 | 22 | Equivalent is distributed under the terms of both the MIT license and the 23 | Apache License (Version 2.0). See [LICENSE-APACHE](LICENSE-APACHE) and 24 | [LICENSE-MIT](LICENSE-MIT) for details. Opening a pull request is 25 | assumed to signal agreement with these licensing terms. 26 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | //! [`Equivalent`] and [`Comparable`] are traits for key comparison in maps. 2 | //! 3 | //! These may be used in the implementation of maps where the lookup type `Q` 4 | //! may be different than the stored key type `K`. 5 | //! 6 | //! * `Q: Equivalent` checks for equality, similar to the `HashMap` 7 | //! constraint `K: Borrow, Q: Eq`. 8 | //! * `Q: Comparable` checks the ordering, similar to the `BTreeMap` 9 | //! constraint `K: Borrow, Q: Ord`. 10 | //! 11 | //! These traits are not used by the maps in the standard library, but they may 12 | //! add more flexibility in third-party map implementations, especially in 13 | //! situations where a strict `K: Borrow` relationship is not available. 14 | //! 15 | //! # Examples 16 | //! 17 | //! ``` 18 | //! use equivalent::*; 19 | //! use std::cmp::Ordering; 20 | //! 21 | //! pub struct Pair(pub A, pub B); 22 | //! 23 | //! impl<'a, A: ?Sized, B: ?Sized, C, D> Equivalent<(C, D)> for Pair<&'a A, &'a B> 24 | //! where 25 | //! A: Equivalent, 26 | //! B: Equivalent, 27 | //! { 28 | //! fn equivalent(&self, key: &(C, D)) -> bool { 29 | //! self.0.equivalent(&key.0) && self.1.equivalent(&key.1) 30 | //! } 31 | //! } 32 | //! 33 | //! impl<'a, A: ?Sized, B: ?Sized, C, D> Comparable<(C, D)> for Pair<&'a A, &'a B> 34 | //! where 35 | //! A: Comparable, 36 | //! B: Comparable, 37 | //! { 38 | //! fn compare(&self, key: &(C, D)) -> Ordering { 39 | //! match self.0.compare(&key.0) { 40 | //! Ordering::Equal => self.1.compare(&key.1), 41 | //! not_equal => not_equal, 42 | //! } 43 | //! } 44 | //! } 45 | //! 46 | //! fn main() { 47 | //! let key = (String::from("foo"), String::from("bar")); 48 | //! let q1 = Pair("foo", "bar"); 49 | //! let q2 = Pair("boo", "bar"); 50 | //! let q3 = Pair("foo", "baz"); 51 | //! 52 | //! assert!(q1.equivalent(&key)); 53 | //! assert!(!q2.equivalent(&key)); 54 | //! assert!(!q3.equivalent(&key)); 55 | //! 56 | //! assert_eq!(q1.compare(&key), Ordering::Equal); 57 | //! assert_eq!(q2.compare(&key), Ordering::Less); 58 | //! assert_eq!(q3.compare(&key), Ordering::Greater); 59 | //! } 60 | //! ``` 61 | 62 | #![no_std] 63 | 64 | use core::borrow::Borrow; 65 | use core::cmp::Ordering; 66 | 67 | /// Key equivalence trait. 68 | /// 69 | /// This trait allows hash table lookup to be customized. It has one blanket 70 | /// implementation that uses the regular solution with `Borrow` and `Eq`, just 71 | /// like `HashMap` does, so that you can pass `&str` to lookup into a map with 72 | /// `String` keys and so on. 73 | /// 74 | /// # Contract 75 | /// 76 | /// The implementor **must** hash like `K`, if it is hashable. 77 | pub trait Equivalent { 78 | /// Compare self to `key` and return `true` if they are equal. 79 | fn equivalent(&self, key: &K) -> bool; 80 | } 81 | 82 | impl Equivalent for Q 83 | where 84 | Q: Eq, 85 | K: Borrow, 86 | { 87 | #[inline] 88 | fn equivalent(&self, key: &K) -> bool { 89 | PartialEq::eq(self, key.borrow()) 90 | } 91 | } 92 | 93 | /// Key ordering trait. 94 | /// 95 | /// This trait allows ordered map lookup to be customized. It has one blanket 96 | /// implementation that uses the regular solution with `Borrow` and `Ord`, just 97 | /// like `BTreeMap` does, so that you can pass `&str` to lookup into a map with 98 | /// `String` keys and so on. 99 | pub trait Comparable: Equivalent { 100 | /// Compare self to `key` and return their ordering. 101 | fn compare(&self, key: &K) -> Ordering; 102 | } 103 | 104 | impl Comparable for Q 105 | where 106 | Q: Ord, 107 | K: Borrow, 108 | { 109 | #[inline] 110 | fn compare(&self, key: &K) -> Ordering { 111 | Ord::cmp(self, key.borrow()) 112 | } 113 | } 114 | --------------------------------------------------------------------------------