# ELEN - Efficient Lexicographic Encoding of Numbers [![Build Status](https://travis-ci.org/ealmansi/elen.svg?branch=master)](https://travis-ci.com/ealmansi/elen) Based on the [paper](https://github.com/ealmansi/elen/blob/master/resources/elen.pdf) by Peter Seymour. ## Installation `$ npm install --save elen` ## Why would I want to use ELEN? ELEN provides a way of textually representing numbers such that their natural order is preserved as a lexicographical order (i.e. alphabetical order) of their representations. Imagine you need to represent numbers textually. A simple solution would be to simply call `num.toString()`. E.g.: ``` 7..toString() // '7' 11..toString() // '11' ``` For many applications, this will suffice. However, notice that the natural order of the input numbers does not match the lexicographical order of the generated strings. I.e.: ``` [7, 11].sort((a, b) => a - b) // [ 7, 11 ] ['7', '11'].sort() // [ '11', '7' ] ``` That's where ELEN comes in. ELEN provides a way of textually representing numbers such that the following property is fulfilled: ``` assert.deepEqual( nums.map(elen.encode).sort().map(elen.decode), nums.sort((a, b) => a - b) ) ``` ## Usage ### In Node.js ``` const elen = require('elen') const encoded = [ elen.encode(0), elen.encode(42), elen.encode(1), elen.encode(-10), elen.encode(5e100), elen.encode(-Infinity), ] encoded.sort() elen.decode(encoded[4]) // 42 ``` ### Browser #### Script Tag ``` ... ... ``` ## Documentation ### Generate and Browse Locally ``` $ npm run docs ``` ### Online Browse automatically generated jsdocs [online](https://cdn.rawgit.com/ealmansi/elen/master/docs/global.html#encode).