2021-05-05 10:13:49 -07:00
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---
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id: 587d7dab367417b2b2512b70
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title: 函數柯里化和局部調用
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challengeType: 1
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forumTopicId: 301232
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dashedName: introduction-to-currying-and-partial-application
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---
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# --description--
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<dfn>arity</dfn>(參數個數)是函數所需的形參的數量。 函數柯里化(<dfn>Currying</dfn>)意思是把接受多個 arity 的函數變換成接受單一 arity 的函數。
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換句話說,就是重構函數讓它接收一個參數,然後返回接收下一個參數的函數,依此類推。
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舉個例子:
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```js
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function unCurried(x, y) {
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return x + y;
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}
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function curried(x) {
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return function(y) {
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return x + y;
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}
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}
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const curried = x => y => x + y
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curried(1)(2)
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```
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`curried(1)(2)` 會返回 `3`。
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柯里化在不能一次爲函數提供所有參數情況下很有用。 因爲它可以將每個函數的調用保存到一個變量中,該變量將保存返回的函數引用,該引用在下一個參數可用時接受該參數。 下面是使用柯里化函數的例子:
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```js
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2021-10-27 15:10:57 +00:00
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const funcForY = curried(1);
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console.log(funcForY(2)); // 3
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```
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類似地,局部調用( <dfn>partial application</dfn>)的意思是一次對一個函數應用幾個參數,然後返回另一個應用更多參數的函數。 這是一個示例:
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```js
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function impartial(x, y, z) {
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return x + y + z;
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}
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2021-10-27 15:10:57 +00:00
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const partialFn = impartial.bind(this, 1, 2);
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2021-05-05 10:13:49 -07:00
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partialFn(10); // 13
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```
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# --instructions--
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填寫 `add` 函數主體部分,用柯里化添加參數 `x`,`y` 和 `z`.
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# --hints--
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`add(10)(20)(30)` 應返回 `60`。
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```js
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assert(add(10)(20)(30) === 60);
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```
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`add(1)(2)(3)` 應返回 `6`。
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```js
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assert(add(1)(2)(3) === 6);
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```
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`add(11)(22)(33)` 應返回 `66`。
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```js
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assert(add(11)(22)(33) === 66);
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```
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應返回 `x + y + z` 的最終結果。
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```js
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assert(code.match(/[xyz]\s*?\+\s*?[xyz]\s*?\+\s*?[xyz]/g));
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```
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# --seed--
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## --seed-contents--
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```js
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function add(x) {
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// Only change code below this line
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// Only change code above this line
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}
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2021-10-27 15:10:57 +00:00
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2021-05-05 10:13:49 -07:00
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add(10)(20)(30);
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```
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# --solutions--
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```js
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const add = x => y => z => x + y + z
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```
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