javascript - の iterator がちょっと非力だったので

function* count(n) {
    for (let i = 0; i < n; i++) yield i;
};

[...count(8)]; // [0,1,2,3,4,5,6,7]

for (const i of count(8)){
  console.log(i);
}

count(8).map(v => v*v).filter(v => v % 2 === 1)

(0..<8).map{$0 * $0}.filter{$0 % 2 == 1}

(0..7).map{|v| v*v}.filter{|v| v % 2 == 1}

[v * v for v in range(8) if v % 2 == 1]

import {Xiterable} from './xiterable.js';
const xcount = n => new Xiterable(() => count(n));
const tens = xcount(10);
const odds = tens.filter(v=>v%2).map(v=>v*v);
const zips = tens.zip(odds);
[...tens];  // [ 0,      1,      2,       3,       4, 5, 6, 7, 8, 9]
[...odds];  // [ 1,      9,     25,      49,      81]
[...zips];  // [[0, 1], [1, 9], [2, 25], [3, 49], [4, 81]]

(0..<8).map{$0 * $0} // この時点で [0, 1, 4, 9, 16, 25, 36, 49]
 が生成される

(0..<Int(1e8)).map{$0*$0}

(0..<Int(1e8)).lazy.map{$0*$0}

xcount(1e8).map(v => v*v)

[...xcount(1e8).map(v => v*v).take(8)]

import { xrange } from './xiterable.js'
xrange().nth(42);  // 41

[...xrange(0,4)];  // [0,1,2,3]
[...xrange(0n,4n)];// [0n,1n,2n,3n]

import { Permutation } from 'js-combinatorics';
let it = new Xiterable(
  new Permutation('abcdefghijklmnopqrstuvwxyz')
);
it.map(v => v.join('')).nth(403291461126605635583999999n); 
// 'zyxwvutsrqponmlkjihgfedcba'