函数式编程知识点笔记

记录学习过程中函数式编程(FP)相关概念

Applicative Functor

示例：

export class ApplicativeFunctor extends Array {
  ap(xs: any[]) {
    const arrs = this.reduce((acc, f) => acc.concat(xs.map(f)), []);
    return new ApplicativeFunctor(...arrs);
  }
}

const app = new ApplicativeFunctor();
app.push(a => a + 1);
app.push(a => a + 2);
app.push(a => a + 3);
console.log(app.ap([1]));
// ApplicativeFunctor [ 2, 3, 4 ]

const app = new ApplicativeFunctor();
app.push(a => b => a + b);
const app2 = app.ap([1, 3]);
console.log(app2);
// ApplicativeFunctor [ [Function], [Function] ]
console.log(app2.ap([4, 5]));
// ApplicativeFunctor [ 5, 6, 7, 8 ]

Comonad

export class Comonad {
    constructor(public val: any){}
    extract(){
        return this.val;
    }
    extend(f:(val:Comonad)=>any){
        return new Comonad(f(this))
    }
}