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談談_Functional_Programming.pdf
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CypressKuo
August 30, 2019
Technology
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談談_Functional_Programming.pdf
CypressKuo
August 30, 2019
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Transcript
談談 Functional Programming CypressKuo @前端組例會 2019/08/30
In computer science, functional programming is a programming paradigm. --wikipedia
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Function 的特色 First-class High Order Function No side effect Referential
transparency Pure Function
First-class 函數與其他數據類型一樣,處於平等地位。 • 被賦值到其他變數 • 作為參數傳入到不同的函數中 • 作為函數的回傳值
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High Order Function 滿足以下兩項其中之一的函數 • 將函式當成參數傳入的函式 • 將函式當成回傳值的函式
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常見的 High Order Function Array.prototype.map(foo) Array.prototype.filter(foo) Array.prototype.reduce(foo) Array.prototype.forEach(foo) Array.prototype.some(foo) Array.prototype.every(foo)
No side effect 沒有與外部互動,產生與運算無關的其他結果。 anti pattern: • 發送 http request
• 印出 console • 取得使用者的 input
Referential transparency 不管外部環境如何,只要參數相同,函式執行的返回結果必定相同。
Pure Function 結合 no side effect 與 Referential transparency 一個
function 給予相同的參數, 永遠會回傳相同的返回值,並且沒有任何顯著的副作用。
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Function Composition Curry Compose
Curry 將一個有 N 個參數的函數轉換成 N 個只有一個參數的函數
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Compose 把兩個以上的一個參數函數合併起來串聯多個組合成新的函數
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Functor 範疇間的一類映射 F(f . g) = F(f) . F(g) (
. 代表 compose) F 就是 Functor
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抽象化 縮減一個概念或是一個現象的資訊含量來將其廣義化的過程
🍎 + 🍎 = 🍎🍎 🍌 + 🍌 = 🍌🍌
(🍎🍎) + (🍎🍎) + (🍎🍎) = 🍎🍎🍎🍎🍎🍎 (🍌🍌) + (🍌🍌) + (🍌🍌) = 🍌🍌🍌🍌🍌🍌 抽象化
1 + 1 = 2 進一步 => fn(1, 1) ->
2 // fn = (a, b) => a + b; 2 + 2 + 2 = 6 進一步 => 2 * 3 = 6 再進一步 => fn(2, 3) -> 6 // fn = (a, b) => a * b; 抽象化
資料與功能分離,不要直接操作資料 抽象化 in FP
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實例
優勢: • 可讀性高 • 可維護性高 • 簡潔,開發快速 劣勢: • 難以入門
優劣
If all you have is a hammer, everything looks like
a nail. 活用工具,不是被工具所用。 結論
Q & A
• https://speakerdeck.com/s6323859/abstract-thinking-cong-functional-programming-k an-jian-cheng-shi-zhi-mei • https://docs.google.com/presentation/d/1ZvBmQlNoeTOxV5oArnOcES-iswSqPovTe Y4hyWz3N0c/edit?usp=sharing • http://www.ruanyifeng.com/blog/2017/03/pointfree.html 參考資料
wish you a nice day!