https://github.com/hexagon6/collatz-wasm

https://github.com/hexagon6/collatz-wasm

Last synced: about 1 month ago
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• Host: GitHub
• URL: https://github.com/hexagon6/collatz-wasm
• Owner: hexagon6
• Created: 2021-08-07T17:34:28.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2021-10-09T21:41:47.000Z (about 3 years ago)
• Last Synced: 2024-05-20T00:14:39.009Z (8 months ago)
• Language: JavaScript
• Size: 10.7 KB
• Stars: 1
• Watchers: 3
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

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README

        
# collatz-wasm

1. pick a positive integer number

2. a) when odd: 3x + 1

2. b) when even: x/2

3. repeat until you find a number you had before

on positive integers this algorithm (the mathematical equivalent is called [Collatz Conjecture](https://en.wikipedia.org/wiki/Collatz_conjecture)) ends always at 1

![XKCD Collatz Conjecture](https://imgs.xkcd.com/comics/collatz_conjecture.png)

> it is an unsolved mathematical problem, but you could give it a try in the browser or another system which can run wasm with this module ;-)

> it accepts any javascript number (internally i32) and gives back an Array of numbers

## usage

By installing from [npm](https://www.npmjs.com/package/collatz-wasm)

`npm install collatz-wasm`

and by using a bundler you should be able to import it in javascript like this:

```javascript

import init, { collatz } from "collatz-wasm"

...

init()

   .then(() => {

      collatz(1337)

   })

```

## plans for the future

I plan on adding support for i64 (javascript BigInt), but have not yet reached a proper understanding of Rust Traits to do so. An alternative would be to copy code and replace i32 with i64, but who would do such a thing??

## uses

The Collatz Conjecture can be used to plot nice graphs and art, which was a motivation to create this module

## building from rust to wasm

### install dependencies

First install a rust environment (e.g. rustup)

and then install wasm-pack like-a-so: `$ cargo install wasm-pack`

### build wasm bundle

> based on this howto: https://developer.mozilla.org/en-US/docs/WebAssembly/Rust_to_wasm

`$ wasm-pack build --target web`

This builds the rust lib.rs into a file bundle at `pkg/` which is ready to be imported into a javascript environment that has wasm support.

### using it locally from the git repository

```javascript

 import init, { collatz } from "./pkg/collatz_wasm.js"

 init()

   .then(() => {

      const list = Array.from(collatz(10))

      console.log(JSON.stringify(list))

   })

```

### test wasm bundle locally

Start a local webserver (e.g. `python3 -m http.server`) and navigate to index.html to see a test page importing the compiled wasm (open Developer Tools to see result logged in the Javascript console).