AoC 2022 Day 25

aoc_2022_day25.js

const pipe = (...fns) => v => fns.reduce((a, f) => f(a), v);
const MAPPING = "=-012";
const parse = input =>
  input
    .split("\n")
    .map(line =>
      line.split("").map(c => MAPPING.indexOf(c) - 2)
    );

const toDecimal = list =>
  list.map(nums =>
    nums
      .reverse()
      .map((num, i) => num * Math.pow(5, i))
      .reduce((sum, v) => sum + v)
  );

const sum = list => list.reduce((sum, v) => sum + v);

const toSNAFU = number =>
  [...number.toString(5)]
    .map(Number)
    .reduceRight(
      ([res, carry], v) => (
        (v += carry),
        [[v > 2 ? v - 5 : v, ...res], v > 2 ? 1 : 0]
      ),
      [[], 0]
    )[0]
    .map(v => MAPPING[v + 2])
    .join("");

export const part1 = pipe(parse, toDecimal, sum, toSNAFU);

Could you explain how pipe works ? I don't understand from where the functions in the pipe get their arguments from