Currying & 柯里化

[xgqfrms]

Currying & 柯里化

https://www.cnblogs.com/xgqfrms/p/14025942.html

函数式编程

https://www.cnblogs.com/xgqfrms/p/5730527.html

https://en.wikipedia.org/wiki/Currying

https://zh.wikipedia.org/wiki/%E6%9F%AF%E9%87%8C%E5%8C%96

https://zh.wikipedia.org/wiki/柯里化

[xgqfrms]

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[xgqfrms]

https://zh.javascript.info/currying-partials

_curry

https://lodash.com/docs#curry

https://github.com/lodash/lodash/blob/4.17.15/lodash.js#L10198

https://github.com/lodash/lodash/blob/4.17.15/lodash.js#L5488

https://github.com/lodash/lodash/blob/ddfd9b11a0126db2302cb70ec9973b66baec0975/lodash.js#L5488

https://www.npmjs.com/package/lodash.curry

[xgqfrms]

The function composition of [f(x), g(x), h(x)] is fn(x) = f(g(h(x))).

[f(x), g(x), h(x)] 的函数组合为 fn(x) = f(g(h(x)))。

https://leetcode.com/problems/function-composition/?envType=study-plan-v2&envId=30-days-of-javascript

type F = (x: number) => number;

function compose(functions: F[]): F {
    // cury // 柯里化
    return function(x) {
        //
    }
};

/**
 * const fn = compose([x => x + 1, x => 2 * x])
 * fn(4) // 9
 */

solutions ✅

type F = (x: number) => number;

function compose(functions: F[]): F {
    // cury // 柯里化
    return function(x) {
      for(let i = 0; i < functions.length; i++) {
        // let func = functions[functions.length - 1 - i];
        // x = func(x);
        x = functions[functions.length - 1 - i](x);
      }
      return x;
    }
};

/**
 * const fn = compose([x => x + 1, x => 2 * x])
 * fn(4) // 9
 */

🚀

// Typescript
type F = (x: number) => number;

function compose(functions: F[]): F {
    return function(x) {
        return functions.reverse().reduce((acc, current) => acc = current(acc), x)
    }
};

/**
 * const fn = compose([x => x + 1, x => 2 * x])
 * fn(4) // 9
 */

[xgqfrms]

https://www.cnblogs.com/xgqfrms/p/11342509.html#4744377

"use strict";

/**
 *
 * @author xgqfrms
 * @license MIT
 * @copyright xgqfrms
 * @created 2020-11-17
 * @modified
 *
 * @description
 * @description
 * @difficulty Easy Medium Hard
 * @complexity O(n)
 * @time O(n)
 * @augments
 * @example
 * @link https://javascript.info/currying-partials#advanced-curry-implementation
 * @solutions
 *
 * @best_solutions
 *
 */

const log = console.log;


function curry(func) {
  return function curried(...args) {
    // log(`func.length =`, func.length)
    log(`args.length =`, args.length, args)
    if (args.length >= func.length) {
      // 以获取全部的参数， 将参数传递给 callback function

      // apply 接受一个参数数组，改变方法绑定的对象后，方法会立即执行 callback function ✅
      // call 接受一个参数列表，改变方法绑定的对象后，方法会立即执行 callback function ✅
      // bind 仅仅改变方法绑定的对象，但方法不会立即执行，需要手动调用方法才会执行 callback function ✅
      // bind, apply, call改变 this 指向
      // ⚠️ 箭头函数，不适用需要使用改变 this 绑定的场景

      return func.apply(this, args);
    } else {
      return function(...args2) {
        log(`args2.length =`, args2.length, args2)
        // 分步获取参数，并将参数拼接到一起
        // 闭包，内部函数可以访问到外部函数的所有属性
        return curried.apply(this, args.concat(args2));
      }
    }
  };
}


function sum(a, b, c) {
  return a + b + c;
}

// ??? @decorator 装饰器-设计模式
const curriedSum = curry(sum);

log(`\n`, curriedSum(1, 2, 3));
// 6, still callable normally
log(`\n`, curriedSum(1)(2, 3));
// 6, currying of 1st arg
log(`\n`, curriedSum(1)(2)(3));
// 6, full currying


/*

// error
const test1 = isValid(`((}}`);
// ok
const test2 = isValid(`()[]{}`);

log(`❌test =`, test1 ? `✅` : `❌`);
log(`✅test ok =`, test2 ? `✅` : `❌`);

*/

???

https://www.cnblogs.com/xgqfrms/p/14025942.html

[xgqfrms]

// bug ❌
// obj = {a: 1, f: () => console.log(`a = ${this.a}`), };


obj = {a: 1, f: function (){ console.log(`a = ${this.a}`)}, };
// {a: 1, f: ƒ}
obj.f()
// a = 1

obj2 = {a: 2}
// {a: 2}
f = obj.f.bind(obj2);
// ƒ (){ console.log(`a = ${this.a}`)}
f();
// a = 2

obj.f.call(obj2);
// a = 2

obj.f.apply(obj2);
// a = 2


/* 


apply 接受一个参数数组，改变方法绑定的对象后，方法会立即执行 callback function ✅
call 接受一个参数列表，改变方法绑定的对象后，方法会立即执行 callback function ✅
bind 仅仅改变方法绑定的对象，但方法不会立即执行，需要手动调用方法才会执行 callback function ✅

bind, apply, call改变 this 指向

⚠️ 箭头函数，不适用需要使用改变 this 绑定的场景

*/

[xgqfrms]

function curry(func) {
  return function curried(...args) {
    if (args.length >= func.length) {
      return func.apply(this, args);
    } else {
      return function(...args2) {
        return curried.apply(this, args.concat(args2));
      }
    }
  };
}

https://javascript.info/currying-partials#advanced-curry-implementation

https://zh.javascript.info/currying-partials#gao-ji-ke-li-hua-shi-xian

const curry = fn =>
    curried = (...args) =>
        args.length === fn.length
            ? fn(...args)
            : (arg) => curried(...args, arg)

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