calc.js

const example = ["+", 1, 2, 3];

const builtin = {
  "+": (a, b) => a + b,
};

const resolve = symbol => builtin[symbol];
const isUndefined = value => value == null;

const car = list => list[0];
const cdr = list => list.slice(1);

const apply = (func, args) => {
  return args.reduce(func);
};

const evl = list => {
  const args = cdr(list);
  const f = resolve(car(list));
  return isUndefined(f) ? args.unshift(f) : apply(f, args);
};

export default {
  eval: evl,
  apply,
  example
};