Dan Dart danwdart

Solving Perfect Numbers Quickly with Haskell

Walking through the stages of optimizing a perfect-number algorithm; starting with a naive approach, rewriting to use the Euclid-Euler theorem, and then leveraging the Miller-Rabin primality test.

A Frustratingly Naive Solution

On a dark and stormy night in Kansas, many years ago, I sat in front of my laptop - face lit only by the screen.

A homework assignment had tasked us with writing a basic haskell function to find every perfect number between 1 and 9000. We weren't studying numbers, nor did we discuss perfect numbers in class. The number "9000" was chosen as the upper limit due to the complexity associated with finding perfects using typical methods.

Talking about Toys

Every year Santa 🎅 brings joy (and presents 🎁) to all the kids in the world. Well, not when I was a child! Following the usual Spanish traditions, the Three Reyes Magos brought me presents in their camels 🐫 following the Star 💫 Nowadays, it's Sinterklaas who puts pepernoten in my shoes 👞. Because in fact there's not one, but a group of present-bringing people, distributed across the globe 🌐, each with their own part of the world to cover (or you really thought just one man and eight reindeers could do it all by their own?)

In order to communicate, they need a way to exchange information about presents. Since they are all very wise, they've agreed to use Haskell, so this information is represented using algebraic data types. Here are some types related to building blocks:

data Block = Block BlockBrand String Color
data BlockBrand = Lego | KNex

Easy Amiibo Emulation - https://bit.ly/2z0m09k

(^ that's a short-link to this page, so you can open it in Linux)

Some users are discussing this guide in #hacking on the JoyConDroid Discord: https://discord.gg/SQNEx9v.

DO NOT ask for, or share links to, Amiibo bins in the comments! They will be removed. Thank you for understanding.

(Windows|Linux PC) + JoyControl + Bluetooth = AMIIBO EMULATION

Statically checked overloaded strings

This gist demonstrates a trick I came up with which is defining IsString for Q (TExp a), where a is lift-able. This allows you to write $$("...") and have the string parsed at compile-time.

On GHC 9, you are able to write $$"..." instead.

This offers a light-weight way to enforce compile-time constraints. It's basically OverloadedStrings with static checks. The inferred return type

General context

A static website using a generator (like Jekyll)
Comments are in a folder, one comment = one JSON file (attached to article based on path + filename)
website is versionned using git, repository hosted by github (cool for pull-requests)

Posting a new comment

OK here we need some dynamism ;)

An ongoing project to catalogue all of these sneaky, hidden, bleeding edge selectors as I prepare my JSConf EU 2012 talk.

Everything is broken up by tag, but within each the selectors aren't particularly ordered.

I have not tested/verified all of these. Have I missed some or got it wrong? Let me know. - A

A friendly reminder that you may need to set this property on your target/selected element to get the styling results you want:

-webkit-appearance:none;

	#!/usr/bin/env nix-shell
	#! nix-shell -p wine -i sh
	wine ~/bin/winbox.exe

	# non nix (dependencies) version

	console.log(1);
	(_ => console.log(2))();
	eval('console.log(3);');
	console.log.call(null, 4);
	console.log.apply(null, [5]);
	new Function('console.log(6)')();
	Reflect.apply(console.log, null, [7])
	Reflect.construct(function(){console.log(8)}, []);
	Function.prototype.apply.call(console.log, null, [9]);
	Function.prototype.call.call(console.log, null, 10);

	const I = x => x
	const K = x => y => x
	const A = f => x => f (x)
	const T = x => f => f (x)
	const W = f => x => f (x) (x)
	const C = f => y => x => f (x) (y)
	const B = f => g => x => f (g (x))
	const S = f => g => x => f (x) (g (x))
	const S_ = f => g => x => f (g (x)) (x)
	const S2 = f => g => h => x => f (g (x)) (h (x))

	<?php

	function compileCPP(string $sourcePath, string $binaryPath): bool {
	$descriptorspec = [
	0 => ['pipe', 'r'],
	1 => ['pipe', 'w'],
	2 => ['pipe', 'w']
	];

	$cwd = '/tmp';