temporalcohesion.co.uk

As promised, here is the first part of the series of posts I hope to write demonstrating how I wrote my problem runner framework for Project Euler.

Firstly, before you continue reading, I suggest that you research the Command pattern, Google will also provide you with some good sources in your research.

Done? Ok then. It shouldn’t matter what IDE you use, I am using Eclipse (ganymede), any IDE should do. If you don’t know what an IDE is, then go and find out, and then come back.

Start Coding

In your IDE, and following the Java package naming conventions, create a package to hold the Project Euler code, for example: co.uk.temporalcohesion.euler.problems. Because we are going to need an interface, also create a package to hold those, as this can help keep things more organised, for example: co.uk.temporalcohesion.euler.interfaces

Let’s define that interface

public interface Problem {
 
	/**
	 * Answer method. Returns the answer for the problem
	 * @return - the integer answer to the problem
	 */
	String answer();
 
	/**
	 * The problem number.
	 * @return - The number of the problem
	 */
	int id();
 
	/**
	 * How long does it take to work out the answer?
	 * @return - The time in seconds it takes to work out the answer to the problem
	 */
	double time();
}

Before we move on an implement that interface in a problem, let’s write the basic problem runner itself. We’ll need a way to register an instance of a problem, and a way to run the problem and get the answer.

public class Euler {
	private List<Problem> problems = new ArrayList();
 
	public Euler() {
		problems.add(new One());
	}
 
	private void run() {
		for (Problem prob : problems) {
			System.out.println("Problem " + prob.id() + ": " + prob.answer());
		}
	}
 
	public static void main(String[] args) {
		new Euler().run();
	}
}

That’s pretty much all you need for a basic problem runner. You just register an instance of each problem you write into the problems List object in the constructor, and run the program, and it iterates through each Problem in the List, and outputs the answer.

I’m not going to give you the code to problem one, however it is pretty trivial if you know what the modulus operator is used for…

As you can see, the problem runner itself is fairly basic, and does present some immediate areas of improvement, such as running a specific problem.

I’ll cover that next time.

Recently, I’ve been working on the problems on Project Euler, and I’ve done the first 16 problems (in Java), although I will freely admit that I had help on two of the most difficult ones. I do intend on continuing to do the problems, and I am currently working on problem 17, however I paused to write the problem runner framework I’m going to talk about in this post.

What I had started to do, was to write each solution in it’s own Class, and have the main(String[] args) method output the answer. This was fine for the first few problems, and I could have continued to do it like that for all of the problems - however I wanted to be able to run all the problems at once, or a specific problem, and get the answer(s), or not show the answers but still get the timings.

After chatting with one of the Senior Dev’s at my job, he pointed out that what I wanted to do was basically the Command pattern. He sent me some example code, although once he’d said “Command pattern” I knew exactly what it was that I needed to do.

Thus, my problem runner framework was born, and whilst fairly simple, it does employ some techniques that the beginning Java developer might not be aware of. So, what I am going to (try) to do over the next few weeks is write a series of posts that show how I wrote it, partly just to have some content on my blog (which I am really, really lazy at updating), secondly to see how good I am at explaining something like this, and thirdly - it might actually be useful to someone.

The output of the problem runner framework looks like this:

C:\development>java -jar euler.jar -noanswers
Project Euler : Problem Runner - http://projecteuler.net/

Problem: 1. Time: 0.0s
Problem: 2. Time: 0.0s
Problem: 3. Time: 0.347s
Problem: 4. Time: 0.307s
Problem: 5. Time: 63.803s
Problem: 6. Time: 0.0s
Problem: 7. Time: 0.335s
Problem: 8. Time: 0.0020s
Problem: 9. Time: 34.178s
Problem: 10. Time: 0.369s
Problem: 11. Time: 1.218275999017E9s
Problem: 12. Time: 0.021s
Problem: 13. Time: 0.0s
Problem: 14. Time: 21.717s
Problem: 15. Time: 0.0s
Problem: 16. Time: 0.0010s

As you can see, I have output a list of the problems, and the time taken to solve the problem, but I haven’t shown the answer.

Well, you didn’t think I was going to tell you the answers… Did you?

This also shows that I need to work on problem 5, 9 and 14 to try and optimise the solution to speed up performance, Project Euler says that problems “should” take under a minute to solve, however I’d still like to improve the code.

It’s true, New Years resolutions are passé. Every year, you look at what is wrong in your life and triumphantly decide that you are going to resolve these problems by issuing a bold and sweeping set of statements, or edicts.

• Lose weight
• Stop smoking
• Get fit

These are what you want to achieve, chasing that ever elusive dream of making your life better. Can you? Can a simple list of statements help you achieve these goals? I’m not so sure. For some people I’m sure that they don’t even have to write them down, those super motivated people who seem to exude success.

I used to do this, on scraps of easily lost paper, “Stuart’s New Year’s Resolutions!” it would say, with a list of two or three word ambition’s for the year. Lost by February. For the last few years I haven’t even bothered with writing them down, I’d just mouth off to anyone who would listen, “I’m gonna do this, and that, this year, you wait and see”.

Which funnily enough, didn’t get me very far with achieving very much. That said, 2007 was a year I’ll never forget, for a number of reasons (not all of which I want to go into here), and it has led me to believe even more than I did, that it is all well and good to strole through life without a care, thinking everything is fine and dandy. Because it is not. Doing that will get you stuck, trapped in a rut that you can’t get out of, never having made anything of your life.

Thankfully, I’m pretty certain that I’m not in a rut. Trust me, I’ve been there and I know what it is like.

So what to do instead of making ‘New Year’s Resolutions’? It’s simple: Set goals. “But”, I hear you cry, “a goal IS a resolution?!” Which in this sense I suppose they are, however there is a crucial difference. A goal set’s out what you want to do and how you are going to achieve it.

The above list could be re-written like so:

• Lose weight by eating healthily and exercising more to get fit.
• Stop smoking by using patches and will power, giving up completely by Easter.
• Get fit, by joining a gym, running and cycling and lose 2 stone by Easter

These aren’t my goals for this year… Ok, I don’t smoke, but the other two count. I’m not revealing my other goals… yet. I have several though, and I intend to get stuck in and achieve them.

Something I discovered fairly quickly when coding (cake)PHP in eclipse, is that, like code completion in Models, unless you do a little extra configuration, code completion in Views won’t work.

If however, you make a slight modification to the Views index.ctp, and create a HtmlHelper() yourself, then you get code completion on $html->, and access to all the methods, and the rendered view isn’t affected at all.

For example:

<?php
if(false)
 
{
 
$html = new HtmlHelper();
 
}
 
?>

I found the answer to this after posting on the CakePHP google group, and getting a good answer from a user. Top Stuff

After chatting with one of my friends who is earning loads of cash doing php web development, I’ve decided that I’m going relearn PHP, not because I want a change of career, I’m happy where I am, but because… I just want to.

Because I’ve become a bit of a snob, used to having intellisense and and all the wonders that IDE’s such as Visual Studio and Borland Delphi provide, I wanted to do my PHP development in a proper IDE. Since I’ve been doing a lot of Java at work - enter Eclipse, and the Eclipse PHP plugins.

As you can see in the screenshot above (which shows some code from the cakePHP 15 minute blog tutorial), the plugins provide an awesome amount of functionality, such as:

• Code folding
• Intellisense/code completion
• Syntax highlighting/colouring
• API Documentation tool-tips

All this functionality is pretty easy to set up, and there is a pretty good guide available in The Bakery that covers just about everything you need to know to get going. There was a little bit of configuration that I did that was slightly different to that guide:

Firstly, I don’t believe that you need to set up cakePHP as a project in order to get the code completion to work. If you expand your project, and right click on your project include paths, you should be on the PHP Include path dialog, in the projects properties. If you add an external folder, and browse to the cake core directory (for me: C:\xampp\htdocs\cake), and click ok, you should now have code completion and all the associated awesomeness in your project, with the added benefit that for any different projects in your workspace, you can set up different versions of cakePHP or (I haven’t tried this though) a different framework such as Symfony.

Secondly, for code completion in Models, you just have to do something like this:

class PostsController extends AppController{var $name = 'Posts';
 
/**
 
* @var Post
 
*/
 
var $Post;
 
...code
 
}

Hope this is of use to somebody

The other day, I watched the Linus Torvalds tech talk at google, which he gave on source control systems. It was mostly (biased) about how great git is, and how other source control systems, with a few exceptions, have mostly got it wrong. This all got me thinking about source control systems I have used.

Now, I use Microsoft’s Visual Sourcesafe every day at work, and let me tell you: it’s shit. The only (slightly) good thing about it, is the integration with VS.Net 2005, which is unsurprisingly very good. I know that I’m not really offering much of an argument as to exactly why VSS is a horrible pile of dog turd, but anyone whose ever used will understand.

Anyway. I digress.

I never really thought that the creator of Linux would be such an engaging and humorous speaker - aren’t stereotypes fun - but he was. It kind of got me thinking about source control. I’ve used CVS and SVN before on a few open source projects I’ve contributed to, or just wanted to get the latest source for.

I’ve mostly only ever used CVS or SVN, arguably the two most popular version control systems currently in use today. Better than VSS in every way, but still lacking quite a lot. For instance it’s a well known fact that merges in CVS are a horrible nightmare, and that merges in SVN aren’t much better. Thankfully I’ve never had to do them. And I know enough about VSS to know that merges are just generally avoided. Like you’d try to avoid an STI.

So, over the weekend (you’ll notice how much of my free time is “over the weekend”) I decided to have a little play with with some distributed version control systems. Now, I’m not going to go on about what one of those is, nor how great they are, as you can use google for that. But suffice to say that they are fucking ace.

I had to discount Git pretty much straight away - for various reasons (development being primary) I’ve installed Winxp back onto my laptop, and I’m playing with Windows Server 2003 R2 on my dev server, so I road tested Mercurial and Bazaar-ng. I spent a great deal of time researching the two systems, and ultimately decided to go with bazaar. I’ve not really got down to much development with bazaar yet, but early results look promising.

After about 10 minutes fannying around, I had Bazaar installed, and a shared repository set-up on my dev server, which I checked out and branched a few times on my laptop (3 branches: dev, testing and stable). With bazaar I can make as many dev branches as I like, for each crazy idea I have, and easily merge them upstream as they become awesomely realised ideas, or deleted and forgotten about like a red-headed step-child.

This is all on my laptop, and I can easily push my working code onto my desktop if I want to code on there, or back onto my server for safe keeping, or publish it on a website. Or any combination of those. I’ll post some more about Bazaar after I’ve been using it for a while.

I spent much of the weekend fucking around installing linux on my laptop. I like linux, it’s free, and there’s loads of cool software available. I tried:

• Ubuntu 7.04
• Fedora 7
• opensuse 10.2

The actual installations themselves went pretty painlessly, just pop the disk in, and boot from it, and click install. These modern installations are pretty cool, not like the good old days of installing redhat/slackware/debian from multiple floppy discs.

The only problem I had was getting my 3Com 3crwe62092b wireless lan pcmcia card to work. What a pain in the fucking arse that was. Ubuntu Feistey Fawn 7.04 wouldn’t even detect it, and Fedora 7 detected it, but it wouldn’t work.

Needless to say, I was getting frustrated at this point, and I downloaded opensuse 10.2, specifically a 44mb network install disk. And fuck me, it asked me for wlan details, and connected to my wireless network first time. Ace.

But - and theres always a but - when it rebooted there was a problem. The wireless stopped working. I managed to get the rest of the installation completed using a wired connection. After some further googling, it turns out that the solution to my problem was to download the atmel-firmware, and copy the *.bin’s to /lib/firmware. Rebooted and the wireless came up straightway. Hurrah!

I suspect that armed with this new knowledge I should be able to install Ubuntu/Fedora and get the card to work on them, but I’m liking opensuse enough that I’m not sure I can be bothered to reinstall a different distribution again.

This is also the reason that linux isn’t ready for the desktop yet - the average person wouldn’t spend time googling and recompiling kernels and installing different distributions just to get wireless working on their laptop. It should just work, with no effort. This is the advantage that windows has over linux, the driver support is significantly better.

But it works for me, so fuck em.

One of the things in Delphi that frustrates me is the inability to match on strings in case statements. For those people who haven’t done delphi before, case statements are very similar to c++ switch statements, and only opererate on ordinal types.. Now I’ve not done any Java, but as I understand it you can’t switch on strings in that language either. You can in c# though.

I think C# is generally better, but that said I have it on good authority that templates are still much better in C++ than generics are in C#.

Anyway, that’s enough rambling. On to the solution.

What you need to do in order to get around this limitation is cheat. Well, it’s not really cheating. The tricks is to use a look up function that accepts a string, one that you are expecting, which you have in a string array. Then all you need do is return which element of the array has been matched, and use that in the case statement.

function TClassName.lookupFunction(lookup: string): integer;
const
  ARRAY = ['one', 'two', 'three', 'four', 'five'];
var
  i: integer;
begin
  for i := 0 to Length(ARRAY) do
    if lookup = ARRAY[i] then
    begin
      Result := i;
      break;
    end
end
 
procedure TClassName.someProc(somestring: string);
begin
  case LookupFunction(somestring)
  1 : //code that does stuff for 'one'
  2 : //code that does stuff for 'two'
  3 : //code that does stuff for 'three'
  4 : //code that does stuff for 'four'
  5 : //code that does stuff for 'five'
end

See! That’s how simple it is.

Maybe in a future version of delphi borland/codegear will introduce native string support for case statements. I won’t hold my breather though.

Welcome to my new website, and my new blog. I’d kind of outgrown the old site, which I’ve now turned into a kind of “here’s my CV” sort of site. Although I am happy in my job.

I’m going to attempt to write more often on here, about a lot of things. I’m still getting things just the way I like them - I’ve still got a few plugins for wordpress to download and install yet. If I get time I might even write my own theme, but considering there are so many already brilliant themes available I might just save myself the time and effort.

Hell, that’s why I’m using Wordpress and not writing my own blogging system.

As an old friend of mine used to say: Onwards and Upwards!