iterit v0.2.0

iterit

Itertools for Future ECMAScript

Installation

$ npm i iterit      # or
$ yarn add iterit

Usage

There're four schemes.

Injure

This scheme can be used in present ECMAScript (ES2015).

import * as it from 'iterit/lib/injure.mjs'

it.range(10)
  [it.filter](x => x % 2)
  [it.map](x => x * 2)

Bind

This scheme is based on Stage 0 "Function bind syntax" proposal. (babel plugin)

import * as it from 'iterit/lib/lib.mjs'

it.range(10)
  ::it.filter(x => x % 2)
  ::it.map(x => x * 2)

Fsharp

This scheme is based on Stage 1 "F# pipeline operator" proposal. (babel plugin)

import * as it from 'iterit/lib/fsharp.mjs'

it.range(10)
  |> it.filter(x => x % 2)
  |> it.map(x => x * 2)

Smart

This scheme is based on Stage 1 "Smart pipeline operator" proposal. (babel plugin)

import * as it from 'iterit/lib/smart.mjs'

it.range(10)
  |> it.filter(#, x => x % 2)
  |> it.map(#, x => x * 2)

Examples

Find all even fibonacci numbers that is less than ten (as a comparison with wu.js)

import * as it from 'iterit/lib/injure.mjs'

// Generate an infinite sequence of the fibonacci numbers.
function* fibs() {
  let a = 0;
  let b = 1;
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
}

const isEven      = n => n % 2 == 0;
const lessThanTen = n => n < 10;

// Log each even fibonacci number that is less than ten.
fibs()
  [it.filter](isEven)
  [it.takeWhile](lessThanTen)
  [it.forEach](item => console.log(item));

The API of iterit is designed to be more compatible with existed ECMAScript API as possible. e.g., it.forEach & Array.prototype.forEach:

Array<T>.forEach(callbackfn: (value: T, index: number, array: T[]) => void, thisArg?: any): void;

it.forEach<T>(
  this: IterableIterator<T>,
  callbackfn: (value: T, index: number, iter: IterableIterator<T>) => void,
  thisArg?: any): void

Find all narcissistic numbers

import * as it from 'iterit/lib/lib.mjs'

let NarcissisticNumbers =
  it.count()
    ::it.filter(x => {
      const digits = x.toString()::it.map(Number)::it.toArray()
      return x === digits::it.map(d => d ** digits.length)::it.sum()
    })

function nthNarcissisticNumber(x) {
  let temp
  ;[NarcissisticNumbers, temp] = NarcissisticNumbers::it.tee(2)
  return temp::it.nth(x)
}

// Log the 10th narcissistic number.
console.log(nthNarcissisticNumber(10))
//= 153