Regular Expression Fractals

Oops, turns out I haven’t had a post in a good long while. Before it gets even longer, I figure that I should take one off my backlog and just write it up, even if it is a little on the shorter side.

Today’s post was inspired by this post on /r/dailyprogrammer a month ago today: Challenge #178 [Hard] Regular Expression Fractals. The basic idea is that you are going to take a rectangular region and divide it into four quadrants, again and again, recording the path as you go (images from that post):


Fractal Invaders

Today’s post is a follow up to Sunday’s post Procedural Invaders. This time around, we’re going to work through two different space filling algorithms in order to eventually generate something like this:


Look and Say

Random quick post today1. Basically, we want to write code to generate what’s known as Look and Say sequence:

To generate a member of the sequence from the previous member, read off the digits of the previous member, counting the number of digits in groups of the same digit. For example:

  • 1 is read off as “one 1” or 11.
  • 11 is read off as “two 1s” or 21.
  • 21 is read off as “one 2, then one 1” or 1211.
  • 1211 is read off as “one 1, then one 2, then two 1s” or 111221.
  • 111221 is read off as “three 1s, then two 2s, then one 1” or 312211.


Procedural Invaders

Today’s post comes from a long line of ‘inspired by posts’ all pretty much leading back (so far as I can tell) to this post by j.tarbell: invader.procedural from 2003.

The basic idea is that we want to generate ‘invaders’ in the style of space invaders. Except we don’t want 10 or 20, we want tens of thousands. So how do we do it? Well, take a look at this:


Chess Puzzles: N Queens

After two weeks, it seems only right that we actually get around to a real chess puzzle. First on the list: Eight queens puzzle.

Specifically, how do you place n queens on an n by n chess board such that no pair of queens can attack one another?


Chess Puzzles 2: Board?

Now that we’ve got Ludum Dare out of the way, back to chess! Last time, we defined all of the pieces, which is all well and good, but what we really need is a board. More specifically, we want something that can:

  • Represent an 8x8 chess board, storing the location of pieces (including the owner of each)
  • Add logic for collisions, so that when moving a piece, you cannot move through others or capture allies1
  • Add rendering code to display the current chess board (must be flexible enough to handle arbitrary glyphs for fairy chess pieces)

I think that’s about enough for the moment. Let’s do it!


Chess Puzzles 1: Get moving!

Here’s something I haven’t done much1: chess puzzles! I’m still not sure entirely what I think about the game in general. There is certainly quite a lot of strategy, which I like, but to really get good at chess, there’s also some amount of memorizing openings and closings. That’s something I’m a little less thrilled with.

Still, it’s the perfect sort of came to work out programming exercises with. It’s a game of perfect information, so you don’t have to deal with what a player knows and doesn’t. The pieces have well defined, regular moves2 There’s a fairly intense branching factor, but not insurmountable–Deep Blue (chess computer) proved that.

Anyways, enough chatter. Let’s play some chess!