g(3)

g3.js

'use strict'

let memo = {}

class B {
    static f(n) {
        return n + 1
    }
    static use_memo = false

    constructor(a, b) {
        this.a = a
        this.b = b
    }

    toString() {
        return `B(${this.a.toString()},${this.b.toString()})`
    }

    convert() {
        if(! B.use_memo) {
            return this.raw_convert()
        }
        if(! memo[this.toString()]) {
            memo[this.toString()] = this.raw_convert()
        }
        let next = memo[this.toString()]
        while(memo[next.toString()]) {
            memo[this.toString()] = memo[next.toString()]
            next = memo[this.toString()]
        }
        return memo[this.toString()]
    }
    raw_convert() {
        if(typeof(this.a) == 'number' && typeof(this.b) == 'number') {
            if(this.a == 0) {
                return B.f(this.b)
            }else if(this.b == 0){
                return new B(this.a-1, 1)
            }else{
                return new B(this.a-1, new B(this.a, this.b-1))
            }
        }else{
            return new B(typeof(this.a) == 'number' ? this.a : this.a.convert(),
                         typeof(this.b) == 'number' ? this.b : this.b.convert())
        }
    }
}

B.f = (n) => { return n + 1 }
B.use_memo = true
const g = (n) => new B(n, n)

let g3 = g(3)
while(typeof(g3) != 'number') {
    console.log(g3.toString())
    g3 = g3.convert()
}
console.log(g3)