iter

Utility library for functional programming based on ES2015 generators that ensures lazy evaluation of possibly infinite ranges.

Examples

Fizzbuzz generator

import { compose, map, range, take } from 'iter';

const fizzBuzz = compose(
  map(n => n % 3 === 0 ? 'fizz' : n),
  map(n => n % 5 === 0 ? 'buzz' : n),
  map(n => n % 5 === 0 && n % 3 === 0 ? 'fizzbuzz' : n),
  range(1, Infinity)
);

[...take(15, fizzBuzz)]
  // => [1, 2, 'fizz', 4, 'buzz', 'fizz', 7, 8 , 'fizz', 'buzz', 11, 'fizz', 13, 14, 'fizzbuzz']

Fibonacci sequence up to the nth number

import { zipWith, tail, take } from 'iter';

const fibonacci = function * () {
  yield 0;
  yield 1;
  yield * zipWith((x, y) => x + y, fibonacci(), tail(fibonacci()));
};

[...take(8, fibonacci())]
  // => [0, 1, 1, 2, 3, 5, 8, 13]

Methods

• assertIterable(iterable)
• compact(iterable)
• compose(...iterables)
• filter(filterFn, iterable)
• isIterable(iterable)
• map(mapFn, iterable)
• pluck(iterable)
• slice(fromIdx, len, iterable)
• tail(iterable)
• take(num, iterable)
• unqiue(iterable)
• zipWith(zipFn, ...iterables)

Inspiration & further reading:

• Laziness is a virtue
• Programs must be written for people to read