Extracting data from a function chain without arrays

Question

This is an advanced topic of

How to store data of a functional chain of Monoidal List?

I am pretty sure we can somehow extract data from a function chain wit

Answer 1

I'll have to admit I haven't read through your linked questions and I'm mainly here for the fun puzzle... but does this help in any way?

I figured you want to differentiate between adding an element (calling with a new value) and running a function on the list (calling with a function). Since I had to somehow pass the function to run, I couldn't get the (1) vs () syntax to work.

This uses an interface that returns an object with concat to extend the list, and fold to run a reducer on the list. Again, not sure if it's a complete answer, but it might help you explore other directions.

const Empty = Symbol();

const L = (x, y = Empty) => ({
  concat: z => L(z, L(x, y)),
  fold: (f, seed) => f(x, y === Empty ? seed : y.fold(f, seed))
});

const sum = (a, b) => a + b;


console.log(
  L(1)
    .concat(2).concat(3).concat(4).concat(5).concat(6)
    .fold(sum, 0)
)