Add Hashable typeclass
還沒有人認領這個 Issue。
評估
- 難度
- 5/5
- 預估耗時
- 一週以上
- 新手友好度
- 20/100
- Issue 類型
- 功能
- 描述清晰度
- 基本清楚
- 活躍度
- 停滯
- 領域
- backend
研究方向
The issue proposes adding a Hashable typeclass to the prelude and deriving support to the compiler, but names no files or tests. Start by reviewing the existing Eq and Ord typeclasses and the linked purescript-unordered-collections implementation. Done means agreeing on the design and adding the prelude typeclass and compiler deriving support; the thread has had no comment for years, so check whether the proposal is still wanted.
由索引模型根據 Issue 內容生成。
描述
I would like to add a Hashable typeclass to the prelude and deriving support for it to the compiler. It is intended as an approximation of equality for use in hash-based algorithms and data structures, such as hash maps, not cryptographically secure digests or password hashes.
class Eq a <= Hashable a where
hash :: a -> Int
There are two reasons for adding it to the prelude instead of having a standalone library:
- Dependencies: To be useful in general data structures, as many datatypes as possible should be hashable. Ideally, whenever a datatype is
Eq, it should also haveOrdandHashableinstances, if possible. Most packages depend on the prelude already.[citation needed] This should make it easier to convince authors to addHashableinstances, because they do not need to add another dependency, all that is required is one more deriving line below the lines forEqandOrd. - Performance: Usually, the main goal of hashing is to avoid expensive comparisons. One could write a generic hash function in terms of
purescript-generics-rep. This would be fine for many applications, but for hash-based data structures etc., the hash function should really be as fast as possible.
I am more than happy to make an initial pull request (based on https://github.com/fehrenbach/purescript-unordered-collections/blob/master/src/Data/Hashable.purs) and work on deriving support.
What do people think?
- 主要語言
- PureScript
- 星號
- 168
- 分支
- 90
- 平均合併
- 3 天 1 小時
- 30 天內合併 PR
- 1
環境準備
- 沒有 Dockerfile 或 Docker Compose 檔案
- 有 Pull Request 範本
- 沒有貢獻指南
從這裡開始
- 先讀完整個 Issue，再讀專案的貢獻指南。
- 在 Issue 下留言說明你要接手 —— 這能避免兩個人做同樣的事。
- Fork 儲存庫，在一個分支上完成修改。
- 送出 Pull Request，並在描述裡引用這個 Issue 編號。
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