credmp

Since switching to github last weekend I have very pleased with it, so pleased that I also have put worklog onto it.

You can find it on the worklog page on github. I also added the documentation to the wiki.

If anyone wants to work on it, please create a github account and I will add you to the list of collaborators

Filed under: Code, Emacs by core
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A while back I advertised I was running my own git repos. Today I switched color-theme-arjen to use github.

This switch will allow anyone to do development on it, to fork it or to just watch it.

Public cloning can be done by issueing the following command:

$ git clone git://github.com/credmp/color-theme-arjen.git

Enjoy!

Filed under: Code, Emacs by core
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It’s been a while since I posted on my blog and there have been some interesting happenings in my life.

First, last week I finally passed my drivers examn. Almost 12 years later then anyone else, but still sooner then some other people :). To actually get a drivers license in The Netherlands now you first pass the examn, then the CBR (the goverment branch that arranges driver tests) sends your result electronically to the city databases. The next day you can go and request a drivers license at city hall, at this point you are still not allowed to drive however. I now have to way 5 days before actually getting my drivers license, but then a new danger will be on the road!

I drove with a very nice organisation called ANWB which I can wholeheartedly recommend. I failed miserably on my first examn; nothing is ever easy

Next up is Kings of Code. eBuddy actually sponsered the event, so pretty much every developer of eBuddy was there listening to the various talks. There were numerous interesting talks:

Peter Paul Koch

I missed out on most of this talk, but PPK had much to say about event handlers. He is quite a natural in giving presentations and everybody I talked to found it very informative (slides)

Folke Lemaitre (Netlog)

netlog.com is one of those sites you hear very little about but then you realise that half the world uses it. A community site much like Hyves or myspace, only not as ugly as those. Folke showed us how they handle scalability of databases and HTML caching. The most interesting part of the discussion was about how they utilized memcached to provide content caching and MySQL read offloading. A two thumbs up presentation from my part.

Mark Birbeck (W3C)

As a representative from the W3C Mark gave an insight into RDFa. I had a long discussion with him afterwards about the feasability of the semantic web.

Nate Abele (CakePHP)

This guy didn’t make a lot of friends during the conference. Apparently the current way to win souls for you PHP project is by telling people how messed up the project lead is for the other project. This talk also spurred a Rails vs PHP ditchotomy (as john resig so aptly called it). Not very productive I think.

Nate Koechley (Yahoo!)

The second Nate was awesome however. He talked about the performance of websites; many things were not new to me but the presentation was awesome nevertheless. I think a lot of the attendees went home with a lot to think about and hopefully it will lead to some better designs on the web.

Open Source Pitches

I didn’t attend most of the OSS pitches, so I have very little to say about this.

Menno van Slooten (eBuddy)

Menno gave a smooth overview on the history of web development and the need to give future web developers education in order to bring the skill level up to the next level.

John Resig (Mozilla)

I spent a fair amount of time talking to John before his talk about processing and some other projects. His talk was about choosing a Javascrip library by comparing 4 different ones. I didn’t find it very usefull, since I have very little to do with Javascript libraries, however a lot of people that I talked to who do have to choose found if very informative. John also showed a project called Sizzle, which he will release soon hopefully.

On a very happy note the Blender Foundation has released it’s second open movie project: Big Buck Bunny. Their website is quite overloaded at the moment, but they also put the movie on Youtube. Very funny and well worth the 10 minutes of my time :). Great job guys!

Filed under: Code, blog, eBuddy, web2.0 by core
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For the first time this year the dutch front-end coders event Kings of Code will kick off may 27th. The company I work for is sponsoring the event, which is awesome!

More awesome then that is the fact that my colleague and buddy, Menno, has announced that he will be giving a talk about the future of front-end development.

Of course I am going to try and capture it all on video, the first time I personally know one of the cool kids on the stage

Good luck menno!

Filed under: Code by core
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It has been some time since I wrote my last post. I wanted to share some updates with my subscribers that might be of interest:

1. I made 2 git repositories available:
   1. 8 Queens game solution
   2. Color Theme Arjen
2. My buddy Menno updated his website with some interesting design background.

Of interest to most people would be that color-theme-arjen is slightly updated and should be used instead of the one provided with the color-theme package.

In order to retrieve the content of a git repository you need to have a working git installation. To retrieve color-theme-arjen you would then do: git clone http://credmp.org/git/color-theme-arjen.git

Filed under: Emacs, blog by core
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I like playing games, from board games to computer games to logic puzzles. However, the type of puzzles that intrigue me most are the logic puzzles that really need a computer to be solved (or perhaps I am too lazy to think them through all the way and a computer is a really useful tool for anyone too lazy to think puzzles through for themselves?).

Luckily for me, one of my colleagues and friends, Menno also likes these types of puzzles and we have been playing the game of ’solve this problem with a computer program’ for some time now. The interesting part of it is that Menno programs in JavaScript while I program in C++, Java or Emacs Lisp.

Some of the puzzles we have tackled up to now include ‘17 square’ and ‘The N Queen‘ problem. With 2 people looking at a problem individually of course yields 2 completely different solutions, especially when the solutions are programmed in 2 totally different languages.

Since these type of puzzles take up a lot of my spare programming time I figured it would make good blog posts and might inspire Menno to post his solutions as well.

The first puzzles I would like to pose is the Eight Queen problem, also known as N Queen, since you can pose it with an arbitrary number really.

The problem states that you have a board of N by N squares on which you want to place N Queens (with the movement restrictions of the chess game, just to be clear) in such a manner that none of the Queens are attacked. This problem has 92 possible solutions of which 12 are unique, the rest are reflections or rotations of the board.

Many approaches will lead to a solution of this problem but I chose to use recursion to solve it and implement it in Java, although I have a partially working Emacs Lisp version as well, but am having some weirdness with the recursion not ending up the way I expected it…

Without further lingering, here is my solution:

package credmp.games;
 
public class EightQueens {
    private int SIZE = 8;
    private int board[];
    private int solutions = 0;
 
    public EightQueens() {
	board = new int[SIZE];
    }
 
    public EightQueens(int size) {
        this.SIZE = size;
	board = new int[SIZE];
    }
 
    public int getSolutions() {
        return solutions;
    }
 
    public void solve(int row) {
        for (int column = 0; column < SIZE; column++) {
            if (is_safe(board[row - 1] = column, row - 1)) {
                if (row < SIZE) solve(row + 1); else print_board();
            }
        }
    }
 
    private boolean is_safe(int column, int row) {
        for (int i = 1; i <= row; i++) {
            int current = board[row - i];
            if (current == column || 
                current == column - i || 
                current == column + i)
                return false;
        }
        return true;
    }
 
    private void print_board() {
        ++solutions;
        for (int i = 0; i < (SIZE * 4 + 1); ++i)
            System.out.print("-");
        System.out.println();
        for (int row = 0; row < SIZE; row++) {
            for (int column = 0; column < SIZE; column++ ) {
                System.out.print(column == board[row] ? "| X " : "|   ");
            }
            System.out.print("|\n");
            for (int i = 0; i < (SIZE * 4 + 1); ++i)
                System.out.print("-");
            System.out.print("\n");
        }
    }
 
    public static void main(String args[]) {
        long start = System.currentTimeMillis();
        EightQueens eq = new EightQueens(8);
        eq.solve(1);
        long end = System.currentTimeMillis();
        System.out.println("Time spent: " + 
                           (end - start) + "ms for solutions:" + 
                           eq.getSolutions() );
    }
}

Filed under: Code, Java, games by core
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A very usefull ‘feature’ of some languages is the ability to store values of different types in the same variable. Although this is generally a ‘bad idea’, since it makes it impossible to check for assignment errors during compile-time.

However, there are cases where it is very usefull; for instance, lets say that you are writing something that stores a key/value pair of data of which value can be any given type, perhaps you are writing a HTTP server where you want to store some objects between requests.

In the Java world everything inherits from Object, making the HttpSession nothing more then a Map of String keys and Object values. In C++ we do not have such a common parent, so we cannot store multiple types into the same map.

In the Boost libraries there is something called boost::any. The easiest way to illustrate this is by showing an example:

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#include <boost>
#include <iostream>
#include <string>
 
int main(int argc, char *argv[]) {
    std::string string = "this is a string";
    int integer = 42;
 
    boost::any test = integer;
    std::cout << "An int: " << boost::any_cast<int>(test) << std::endl;
 
    test = string;
    std::cout << "A string: " << boost::any_cast<std::string>(test) 
              << std::endl;
 
    try {
      int no = boost::any_cast<int>(test);
    } catch (boost::bad_any_cast &amp;ex) {
      std::cout << "Cannot cast a string to an int: "
                << ex.what() << std::endl;
    }
}

As you can see, the variable test, which is of type boost::any, can contain any other type and can easily be cast back to the original type (lines 9 and 12). Casting a boost::any to an inconvertible type will cause a boost::bad_any_cast.

Filed under: Code, boost, c++ by core
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Yesterday, ironically the first day of my vacation, I was reading Steve Yegge’s blogpost about code’s worst enemy.

I often find myself intruiged by Steve’s blogposts, probably one of the few blogs on the Internet actually worth reading even if he is talking about something that does not interest you. When it comes to technical writings I often find myself in agreement with his ramblings, however the last blog post sits a little weird with me.

He starts by saying that the size of a codebase (the Lines Of Code, LOC for short) is possibly one of the worst things that can happen to a code base. Later on he starts ranting about Java in particular (seeing that his pet project, which suffered this ailment, is written in Java).

On one hand I have to agree, code bases which are very large (500K LOC as in his example) tend to be quite nasty to deal with, but I would have to disagree that this is the worst thing that can happen to code.

I have come across a lot of programmers in my own career, ranging from people who just started in this industry to well trained coding athletes who are versed in many different languages. The thing I notice most is that complexity is the key factor in making code bases unmanageable.

Young guns in our industry generally tend to write very complex code while the trained athletes choose to reduce complexity by keeping it simple. I guess this is just a learning process everyone goes through, when you are young you never have had to go back a few months/years after writing the code to do some alterations on it ;).

Having many lines of code to deal with is not a problem, as long as it is not too complex. Over the last few years I have also seen a lot of JavaScript code that is just too complex and thus too hard to handle by most minds, even though it did it in way less lines, so I don’t think rewriting a piece of software in a dynamic language just for the sake of reducing code size is the answer to anything.

The key to manageable code bases is a good coding athlete who has the discipline to keep it simple (and of course unit tested).

Filed under: Code by core
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With the release of Emacs 22 on June 2nd a new set of version control (vc for short) modes was released as well. The Emacs Tour briefly touches on it, however it fails to point out the geniusness of this feature.

As of 22.1.1 the following version control backends are supported: RCS, CVS, SVN, SCCS, Bzr, Git, Hg, Arch and MCVS. All commands work the same for all backends.

First, lets start with a link to the full documentation of this feature, the Emacs manual pages. These pages contain all the info in this blogpost, as well as a lot more!

Now, lets take a look at the global keybindings. These keybindings are usable whenever you are visiting a version controlled file (Copied over from EmacsWiki).

There are only a couple of keybindings to remember for day to day usage; C-x v i, C-x v v, C-x v =, C-x v l, C-x v m and C-x v g

Adding files

When you are adding a new file to your project, the C-x v i keybinding takes care of doing it properly for you.

The next action thing

The keybinding C-x v v performs the ‘next action’, this means it will look at the context of the file and will determine the next probable action for the file. When using SVN for instance, after I edit a file, the ‘next action’ will be to do a commit of that file. Some backends checkout their files in read only mode and thus the ‘next action’ is to unlock them and after that the ‘next action’ would be to commit the changes.

It turns out to be a very intuitive way of working with vc and it removes any problem you might have with learning new commands to do the same thing in different backends.

The revision log

The keybinding C-x v l will split the window and will show you a buffer with the revision history of the file. All in all not too exciting, until you read what you can actually do in that buffer. Inside the buffer the keys p and n move you to the ‘previous’ and the ‘next’ entry in the revision log. Pressing d on a revision will show you the Unified Diff of that revision compared to the previous one, so you can see exactly what changed in that revision. The diff feature turns out to be extremely usefull when working in large projects with many people.

Updating a file

If your file is out of sync with your repository just press C-x v m and you can update the file to the latest revision, just press RET. If you pass along a branch number to update to, then all changes from that branch are pulled in.

Seeing changes

To quickly see the changes you have made locally compared to the latest version in the repository, just press C-x v = and a unified diff will pop up.

Who is to blame?

My personal favorite feature of them all, the annotation. Pressing C-x v g will bring up a buffer annotating the current file. By default it will colorize the output depending on age, 18 colors for 20 day steps. So the older the line, the darker the color (default reddish to blue), with steps of 20 days.

There are several keys you can press in this buffer:

Version Control is probably one of the cooler features of the new Emacs (22.1) and it deserves a lot more attention then it is getting at the moment.

Filed under: Code, Emacs by core
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The company I work for eBuddy (blog) has found its way onto the Google Zeitgeist for 2007 as the 7th fastest rising search term for 2007 globally. This is of course massive news, only further confirming the popularity we have among the Internet folks.

Here is the actual image with all the results:

These results are also referenced by sites like Techcrunch but sadly they only report the fastest rising terms in the US…. (I just thought the Internet was a global thing?)…

Cool as this may be, it does pop the question ‘Has the address bar been obsoleted by the consumer?’. When I look around me, all the non-technical computer users seem to put a portal site as their start page, meaning each time they open a browser, they are confronted with a portal site. In The Netherlands, the site startpagina.nl is wildly popular.

If people don’t find what they are looking for on such a portal site, they just type the site name into the search box on the portal site, which most of the times is Google or Yahoo.

This basically means that companies actually need to invest some time and money in Search Engine Optimization if they want to be the top hit when the user performs their search.

Anyways, is the address bar obsoleted by consumers? I don’t think most of them knew what it was anyways; a big bar with lots of slashes and weird words like www and .com/.nl etc… they just want to go to the site called ‘ebuddy’ and do not want to type anything else I guess

Filed under: eBuddy, web2.0 by core
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