class Func {

  constructor(f) {

    // this.run = f

    this.run = x => f(x)

    // this :: Cat (x ↣ y)

    // Cat (y ↣ z) -> Cat (x ↣ z)

    this.pipe = g => new Func(x => g.run(this.run(x)))

    // utility function that pipes Func to a normal function

    // this :: Cat (x ↣ y)

    // (y -> z) -> Cat (x ↣ z)

    this.pipeTo = g => new Func(x => g(this.run(x)))

  }

}

// Cat (x ↣ x)

Func.id = new Func(x => x)

​

​

// usge example:

​

const a = Func.id.pipe(new Func(x => x * 2)).run(10) 

const b = new Func(x => x * 2).pipe(Func.id).run(10) 

​

console.log(`id ⋙ cat : ${a}`)

console.log(`cat ⋙ id : ${b}`)