Why bitbucket is great
Feb 24, 2012 - 05 p.m.

Version control is the software miracle that nobody seems to know about until they get their first job. I've read plenty of forum posts from computer science students asking "What don't they teach you in school?", and inevitably the first response is about version control. It was true for me.

Even for solo development VC is great, and since I've known about it, I've hosted all of my code in a private Subversion repository. This makes working on my code from anywhere easy, and has the added benefit of keeping a backup of my work.

Just as I was becoming comfortable with Subversion, newer distributed version control systems popped up. As the hype around both Git and Mercurial grew, I decided it would be in my best interest to bring myself up to speed. At work we considered switching to Mercurial, mainly on the grounds that it had wider operating system compatibility, so I created myself a Bitbucket account to aid in learning. At the time, Github was exclusively git, and Bitbucket exclusively mercurial.

Both Bitbucket and Github brand themselves as "social coding" websites, but even as I began to use my Bitbucket for all my non-private projects, I never really thought about it. My main reasoning for using it was as an added facet to my resume. Because of the nature of programming, it is sometimes difficult to express your ability level, especially in an interview. Being able to point someone at a big pile of code you've written is helpful.

I really discovered why the "social" aspect of these sites is a big selling point a couple of weeks ago. I posted about GreyHolder, a little jQuery plugin that I wrote and released on my Bitbucket. What I didn't realize was that is contained a bug that could potentially throw away user input. Not very cute behavior for something that is supposed to make life easier on the user. I didn't notice the bug, but my friend Dan did. Because the code was on Bitbucket, he was able to grab it, fix the bug and then send me a pull request to grab the fix. That meant that all I had to do to fix the problem was click a button accepting his new code.

I don't know if you've ever fixed a bug with the press of a button, but it's great, and it should be (and is) the main selling point for code hosting sites. That capability is the reason I'm going to be using code hosting for all my future projects, even the private ones.
Some thoughts on Facebook
Feb 17, 2012 - 05 p.m.

I've never been the biggest fan of Facebook. I have an account, and I check in on it occasionally, but it has never really rubbed me the right way. Why that was the case wasn't clear to me until recently.

Facebook reminds me of AOL. When internet penetration was really ramping up, but before broadband was widely available, AOL was the way that almost everyone got online. AOL wasn't (isn't?) just internet access, it was an entire monolithic internet user experience. For most people, AOL email, AOL chatrooms, AOL instant messaging and AOL content was the internet, and the AOL internet was not very compatible with the rest of the internet. This is what Facebook reminds me of.

Facebook seems to be aiming for the same all encompassing online experience. Facebook can feasibly replace your email, twitter, instant messager, blog, photo sharing service and any online games you might play. There have also been changes recently to try and make facebook your source for news. I suppose all of this is convenient for the user, but I don't like having my entire online presence tied up with one company. Not only does it give them a lot of power, but it nudges you into using whatever implementation of a given technology they are pushing, with no mind to quality. I don't mind facebook keeping track of my friends comings and goings, but when it comes to disseminating information, I prefer twitter. I'd rather maintain my own blog and use a third party instant messaging client because while those service are on facebook, other services do them better.

When I look at the online presences of prominent technology people, they also seem to be spread across different services, picking and choosing the ones that they like, and unlike facebook, I can still check them out without strapping into the service they use. While part of the reason people are so locked into facebook is the lower technological bar for entry, I think as people become more savvy and other services become easier, facebook will start to lose some traction.

Now, AOL is still around, but in an extremely hobbled form. Will the same thing happen to facebook? It doesn't seem super likely, but at the peak of AOL, it didn't seem very likely they were going very far either. AOL had the misfortune of being struck down by broadband, and maybe facebook will have it's own broadband come and strike it down. Perhaps everyone will just leave. Tough to say.
A jQuery plugin
Feb 8, 2012 - 01 a.m.

The other day, in line with my goals for the year, I was working on my family gift distribution project White Elephant. One of my goals for the project has been to push myself toward better page and user interaction design. I've always been a back end sort of guy, telling myself that because I had the know how to code things that I had no reason to care about how those things looked or felt to a user. I've come to realize that assumption is pretty stupid. Taking time to not only make things look pretty, but also make them easy to use is what sets apart outstanding projects from the crummy ones. At this point, I'm a ways from creating the cool things that I want, so actively making myself practice is a step in the right direction.

So back to the main point. I was putting a very stripped down form into a confined space, and instead of having a label next to each input, I thought it would be neat to have some greyed out text that told the user what went in the box. When they clicked the input, the text would disappear and the text they typed would look normal, not greyed out. If you clicked away without typing anything, the original hint text would come back. It looks like this:

I thought it was a clever solution, and that perhaps others would like to use it, so I wrote it as a jQuery plugin. This was a process that took me through the weird world of javascript objects and closures. Things I've touched before, but they always seem a little weird. I found the tutorial on writing jQuery plugins very helpful, and quite instructive about javascript objects as well. You can get the plugin from my bitbucket.

Rotating String
Feb 2, 2012 - 04 p.m.


I was planning on doing an implementation of a B-Tree this week, but instead I've managed to contract a terrible cold and don't really feel like doing much. Instead of a B Tree, here is another quick puzzle from Programming Praxis. Given two strings, the code must determine if the second is a rotation of the first. For example "ttes" and "stte" are rotations of "test". Here is a bit of code:

def rotate_eq(string1, string2):
    if len(string1) != len(string2):
        return False
    start = string1[0]
    length = len(string1)
    match = False
    for i in range(0, length):
        if string2[i] == start:
            match = True
            for j in range(i, length + i):
                #print "does ", string2[j % length], " equal ", string1[j - i]
                if string2[j % length] != string1[j - i]:
                    match = False

First, the strings must be the same length. After that, I search for first letter of the original string in the second. It then cycles through the rest of the string using offsets and modulus to properly rotate through the strings and compare every character.

After solving it the hard way, I looked at the given solution. It turns out if you double up the original string, any rotation of that string is contained in the new double version. Quite clever, and rather simple to code up:

def rotate_eq2(string1, string2):
    if len(string1) == len(string2):
        temp = string1 + string1
        if string2 in temp:
            return True
    return False

It makes my original version look like overkill. You live, you learn. You can get the source on Bitbucket.
Knight's Traversal 2
Jan 26, 2012 - 09 p.m.


So remember a week ago, when I wrote a bit about some code I had written to solve the Knight's Keypad Traversal problem over at Programming Praxis? Sure you do. It's the last post I wrote. Go read it if you haven't.

Anyway, my solution used recursion, and was not the best solution because the complexity of getting the answer grew exponentially. I did not understand fully the better solution, so this week, I made it my business to understand it. I also decided it would be a good time to try and write some code in Ruby, for reasons which are clear to no one. (Notes on Ruby: Arrays seem far too difficult to create.)

The correct solution is the Dynamic Programming solution, which basically means we collapse the problem into smaller subproblems that are faster to solve. Bear with me here, as I've just finished grappling with this solution myself. I personally got a lot out of this stackoverflow answer. Like the recursive solution, we find the base case, which for this problem is the length of a single step path, and we solve it for every position on the key pad. By adding those single step path values together, we can determine the length of a two step path. When you start on one and step to either six or eight, you have one step left, and the know the length of a one step path from any number already, so you just add those together.
i.e. [two step path from one] = [one step path from 8] + [one step path from 6].
Here is a chart that illustrates the first two rows:

1 2 3 4 5 6 7 8 9 0
1 1 1 1 1 1 1 1 1 1
2 2 2 2 3 3 2 2 2 2

What makes this faster than the recursive solution is that we build up from the base case and each successive case is just a bit of quick addition with the previous steps answers. Here is some code.

paths = [
        [4, 6], #0
        [6,8], #1
        [7,9], #2
        [4,8], #3
        [0, 3, 9], #4
        [], #5
        [7, 1, 0], #6
        [6,2], #7
        [3,1], #8
        [4,2] #9

n = ARGV[0].to_i

counts = Array.new(n + 1) { Array.new(10) { |i| i } }

(0..9).each do |i|
    counts[1][i] = 1

(2..n).each do |number|
    (0..9).each do |digit|
        sum = 0
        paths[digit].each do |from|
            sum += counts[number - 1][from]
        counts[number][digit] = sum

puts counts[n][1]
(on bitbucket)

I hope that it is fairly straightforward to see. I've found Ruby easier to read than to write so far. For every path length, we just check on step back in our array of previous answers and add together what we find. It is also quite zippy when compared to the recursive version. One is in python, the other ruby, so the comparison is sort of moot, but just for kicks:
[phil@philsmacbook:random-bits ]$ time python knight_keypad.py 10

real    0m0.346s
user    0m0.017s
sys     0m0.018s
[phil@philsmacbook:random-bits ]$ time ruby knight_keypad.rb 10

real    0m0.047s
user    0m0.003s
sys     0m0.004s

(I tried to run 100, but I think the recursive version is still going.) Pretty cool stuff. Let me know if this post doesn't make a lot of sense... I'm still learning to explain technical things, and since this is something it took me the better part of a day to understand, it might not be perfectly clear. Enjoy.