Planet Open Ghana

Odzangba Dake: The Hunt Continues…

2008-07-01T10:38:54+00:00

Since yesterday, I’ve been looking for a collection manager for my videos. I want something similar to Amarok’s functionality… for video. I’ve tried a few so-called ‘collection managers’ but they simply did not fit my designs. Tellico. GcStar, Elisa… nope. All of these require you to manually enter entries for each video file and only GcStar came close to allowing you to play the video from within the manager (technically, it called up mplayer but that’s okay). I have tons of music videos, tv shows, movies… and I want to just tell the app “this is the folder in which all my videos live” and let it handle the rest. Yeah I know, I’m, lazy.

I especially want playlists for my music videos and I also want a ratings system… sigh. I guess I’ll just have to keep looking. I’d really appreciate a few hints though.

Odzangba Dake: Frustrations…

2008-06-30T07:56:46+00:00

First, I am annoyed… very annoyed. Now on to why I am annoyed. I tried out the piece of crap encryption software called Conceal or something like that. It was supposed to provide one-click encryption. When I tried to encrypt something on Friday, it just showed me a progress bar for four hours and deleted almost all the files in my home folder. Luckily, I’d done a backup the night before so no real damage was done. But enough damage was done to annoy me. I’d mirrored about 8gb of the hardy repositories… I lost that. So now I’m gonna have to stay here in Winneba for another two weeks to re-download all those packages.

Odzangba Dake: Synaptic proxy configuration problems

2008-06-25T18:25:12+00:00

Synaptic gave me at least 15 minutes of pure unmitigated frustration this afternoon when it started choking with this piece of gibberish:

407 Proxy Authentication Required

I’d already configured my proxy settings in apt.conf and my bashrc file, and had assigned the right values to the http_proxy and ftp_proxy variables, not to mention the fact that synaptic had been working okay earlier in the day with no problems so this came as a surprise. Just to make pin-point the problem, I dropped into the terminal and did a sudo apt-get update… worked fine. Tried installing something with apt-get… worked. Tried downloading something with wget… worked fine. Yet synaptic would still not work.

In the end, I tracked down the problem to gksu. When I launched synaptic like so

gksudo synaptic

The problem just disappears and synaptic works… weird. So I used the Alacarte menu editor (right-click on the menu icon and select ‘Edit Menus’) to change the entry for synaptic package manager from

gksu /usr/sbin/synaptic

gksudo /usr/sbin/synaptic

I don’t know what caused this problem and I probably should file a bug report somewhere…

George Gyau: Life in India

2008-06-18T15:43:21+00:00

Life elsewhere outside ones own native country is sometimes great and fun. But somtimes too it becomes like been in hell. And every single person in a country not of his/her native will bear witness this.
I have lived here for almost seven (7) months. And i decided never to blog about this place. But i think sometimes one need to express how they feel for been in a different place.

Language is really one fustrating thing, as today there was a hindi song been played and everyone starts to laugh and i ask for the meaning and everyone keeps tossing me around. As no one wants to really explain to me what the meaning of the song is. Mean while everyone keeps laughing aloud.
People might see it as nothing, but i guess today might be counted as one of the bad times of my stay here.
Life goes on still and as they say is one of the experiences of a foreigner.

Odzangba Dake: What to do when you lose your password

2008-06-07T17:41:08+00:00

Disclaimer: This how-to details procedures for gaining root access to linux boxes. If the linux box is not yours, get the (written) permission of the owner… it’ll save you a lot of trouble. I will not be responsible for anything illegal you do with the stuff you learn on this page.

Okay, so you lost your password? It’s not the end of the world. But first you need physical access to the box.

1. Boot the machine (and press escape at the GRUB menu loading stage if the menu is hidden).

2. Select the correct entry for booting into your linux system - it usually is the first item and is probably already selected - and press “e” on your keyboard.

3. Select the line that begins with root and press “e”on your keyboard to edit it.

4. Look for ro and change it to rw. Now navigate to the end of this line, leave a space and type:

single init=/bin/bash.

5. Press “enter” then “b” on your keyboard and wait for the system to boot and give you a command prompt.

6. Now you need to use the passwd command to change your password. Do:

passwd $user

Replace $user with your username

7. Enter and confirm a new password when prompted, and reboot the machine with the reboot command. I sometimes get an error message when I try to reboot; if you run into the same problem, just turn the pc off and back on.

8. That’s it, you’re good.

Odzangba Dake: Re-building My Local Ubuntu Repository

2008-06-02T13:43:31+00:00

Hardy Heron was released about a month ago and I’m still going through the painful process of mirroring the ubuntu servers. It’s been slow going here and it might take me another month to get the major stuff on my hard disk. Then I’ll make to full transitition to Ubuntu 8.04.

George Gyau: Drupal Links

2008-06-02T10:05:14+00:00

Drupal is a very powerful content management system (CMS). But it can be very confusing and fustrating to start with and get documentations.
I have been working on some drupal projects for the past 2 weeks. And i have really come a long way getting some documentation links on Drupal. So i have decided not to allow people also go through by parcelling all the documentation links i came across on the web and also got through the IRC.

And i will be updating each time somthing new comes up

For Drupal Clean URLS
http://drupal.org/node/15365

Flash Video in Drupal 5: A complete multimedia tutorial
http://www.travistidwell.com/flashvideo

George Gyau: How to zip files on linux

2008-06-02T09:55:40+00:00

Ziping files on linux using shell is one of the most easy things to do
but today i got a bit confused when a friend asked me how to zip a file with
a different name.
example : normally i zip with the source and target name all been same.

zip -r foobar foobar

which will result in

foobar.zip

but what my friend wanted was having a different name for the result.

So i had to jump straight to the linux channel on IRC. below is what i learnt from there.

zip -r foo.zip bar

which results in foo.zip

what abt unziping too

unzip foo.zip

but what about unziping to have different name .

unzip foo.zip && mv foo bar

George Gyau: Howto enable wireless on ACER 4520 on Ubuntu Hardy

2008-06-02T07:13:59+00:00

Just today i had all my configurations for my wifi card which is
Atheros Communications Inc. AR242x 802.11abg Wireless PCI Express Adapter (rev 01) wiped of after a Hardy upgrade. So below i fixed it. But i used it also for the first time when installing Hardy fresh.

1. Open you terminal

2. Get this version of madwifi:

wget -c http://snapshots.madwifi.org/special/madwifi-ng-r2756+ar5007.tar.gz

3. Untar the downloaded package:

tar xvf madwifi-ng-r2756+ar5007.tar.gz

4. Get inside the unpacked directory:

cd madwifi-ng-r2756+ar5007

5. If you haven’t compiled anything from source before on your linux then you propably need the build essential package:

sudo apt-get update && sudo aptitude install build-essential

6. Now you can build your madwifi and install the modules:
make

sudo make install
sudo modprobe ath_pci
sudo modprobe wlan_scan_sta

The last 2 commands can cause some complications on some systems. If they do check your System >> Administration >> Restricted Drivers Manager and disable atheros here. Then try again.

7. Now restart your computer and you should be able to see any aviable networks in your Network Manager.

Joachim Breitner: My first OpenStreetMap Contribution

nomeata — 2008-05-27T15:51:29+00:00

Yesterday I was visiting the Open Source Expo Karlsruhe, a new, quite small conference, at which the guys from OpenStreetMap hat a booth. I was amazed by the progress of OpenStreetMap while I wasn’t looking (which is just a few months, I guess); their level of detail in some places like Karlsruhe is astonishing.

Anyways, I got hooked and started to try out some of the tools and websites and finally, by tracing the Yahoo satellite image, added my first way to the map: A small footpath in Herrenberg that I know quite well:

The live data can also be seen on the OpenStreetMap map, of course.

Unfortunately, there is not much to map around where I live in Karlsruhe, even the driveway to my dorm is included, but maybe I can do some proper mapping (with a GPS device) in Herrenberg someday.

George Gyau: Installing Ubuntu7.10 on Acer4520

2008-05-27T07:35:00+00:00

System Specs
………….
Acer Aspire 4520
AMD64 Athlon X2
Nvidia GeForce 7000M
160 Gig
802.11b/g WLAN
1Gig DDR2

I have been trying for the past weeks since i had this laptop with
the above specs to run ubuntu7.10 but all failed. So i finally got myself
into runing 7.04 rather. But have finally gotten a way to run 7.10 on it and
this is how i did it.

I realised that anytime i installed the 7.10 and i reboot, it hangs at the splashcreen and so for some reason i felt it might be the menu.lst file so edited couple of times but nothing happened. so WHat i finally did was to get the 7.04 ubuntu cds and install and upgrade that to 7.10. And that worked. But when i upgraded the kernel to the original one used by 7.10, i got the same splashscreen hanging again. So i kept the upgrade on but now uses the 7.04 kernel rather instead of the 7.10 kernel which still works fine for me.

But after that, it wasnt all dont since it could not detect some of my hardware devices like the wireless and vga card.

1. to fix the X.
………………

I used the ubuntu livecd and mounted the installed my root(/) partition to get aaccess to xorg.conf file. commands below.

> mkdir /media/system
> mount /dev/sda1 /media/system

The above could be different for you. i mean the mount points

> cd /media/system
> vim etc/X11/xorg.conf

Once you are in this file, look for this lines

Section “Device”
Identifier “nVidia Corporation NVIDIA Default Card”
Driver “nvidia”
BusID “PCI:0:18:0″
EndSection

change the “Driver nvidia” part to “Driver vesa” instead and save and
reboot without the livecd.

2. how to fix sound too
………………………
simple first download the packages from the below site and copy them into one folder

http://www.alsa-project.org/main/index.php/Download

you need one of the c libraries and curses libraries for this i guess you are done with adding extra repositories if not message me i will explain

open the terminal and fire the following
sudo synaptic

and next search for g++ library

after that search for curses library for c

after this automatically done by the synaptic

go the folder where you have downloaded the packages and extract each and everything like below

> tar xjf alsa-(name of the package)

after extarcting just type this

> cd alsa-(extracted package)

> ./configure

> make

> sudo make install

do the above for all packages u just downloaded from the above link.
and afterward just reboot ur machine. u should hear sound now

3. howto fix wireless
………………….

Before we start, we have to make sure that MadWifi drivers don’t get loaded at boot, since we could have a conflict between the two. You can do this typing this:

blacklist ath_pci

in /etc/modprobe.d/blacklist file or by using the restricted driver manager:

> vim /etc/modprobe.d/blacklist

Install ndiswrapper
> sudo apt-get install ndiswrapper
> sudo apt-get install ndisgtk

you can also install ndisgtk or use synaptic instead of the console

after, download the Atheros driver
form this link http://www.atheros.cz/download.php?atheros=AR5006EG&system=1
anyway that is the link i used in getting mine to work.

afterwards you need to unzip the file just downloaded from the link

Install the .inf file in ndiswrapper, using ndisgtk or the command
> sudo ndiswrapper -i net5416.inf
from the unzipped file

Save ndiswrapper module configuration files by issuing the command:
> sudo ndiswrapper -ma && sudo ndiswrapper -mi

You can now reboot and bravo. u can check to see u should be done now.

George Gyau: Web users ‘getting more selfish’

2008-05-27T07:06:42+00:00

Web users are getting more ruthless and selfish when they go online, reveals research. This was made known by usability guru Jakob Nielsen in an annual report into web habits.
I think now people have fair idea as to what really they want or looking for on the web. Is not like sometimes back where people dont really know what exactly they want and so spend so much time on the web.
And in so doing, web users have become very impatient.

Henry Addo: A Fetish Priest With A Website

2008-05-22T14:49:22+00:00

This is so cool. I stumbled upon this website when I was reading an article in a forum post about a pastor being mad at people because he had an issue with a fetish priest. I’m so impressed about this man-Kwaku Bonsam the fetish preist, taking his job a step further by getting a website to [...]

Henry Addo: E-zwich-Easy Banking For Everyone

2008-05-20T10:10:55+00:00

The current hype on the media now is the e-zwich payment system. Quoting from their website, e-zwich is the brand name for the common platform (the National Switch) that links the payment systems of all banks, savings and loans companies and rural banks in Ghana.It is an electronic platform that enables LOADING and SPENDING of e-cash [...]

George Gyau: How to install perl modules through CPAN on ubuntu hardy server

2008-05-19T13:53:42+00:00

This assumes that you have grabbed a copy of the ubuntu hardy server
cd from the ubuntu.com website.

1. Install all dependent packages for CPAN
sudo apt-get install build-essential

2. invoke the cpan command as a normal user

$cpan

But once you hit on enter for “cpan” to execute, you
be asked of some few questions. To make it simple for
yourself, answer “no” for the first question so that
the latter ones will be done for you automatically.

3. Once the above is done, you will be present with the cpan
prompt. now enter the commands below

make install

install Bundle::CPAN

4. Now all is set and you can install any perl module you want. examples of what installed below

cpan prompt> install IO::File
cpan prompt> install Net::SMTP_auth
cpan prompt> Email::MIME::Attachment::Stripper
cpan prompt> Mail::POP3Client

Joachim Breitner: FrakView: An Haskell Renderer for Iterated Function Systems

nomeata — 2008-05-17T12:31:10+00:00

For a recent university seminar, I wrote a haskell program to render and edit iterated function systems (IFS), which generates a certain class of fractals, namely self-similar sets. I think the result is quite nice, so I’m sharing the code.

With FrakView you can view a rendering of the attraktor of the IFS, whith a choice of two algorithms (a straight forward, and a probabilistic), configurable depth and anti-aliasing. You can also modify the IFS by dragging the colored boxes with arrows you see on the screenshot. For the academically inclined, there is also support to visualize cylinder sets and otherwise explore the coding space of the IFS a bit.

The program is written in haskell and uses gtk2hs, the gtk bindings for haskell. It might be interesting for other gtk2hs programmers to see how FrakView solves some issues: For example, it uses the CoroutineT monad transformer I recently blogged about – check out the pausingForM_ function in GUI.hs. Also, the current state of the screen is in one algebraic data type (ScreenConfig) that supports equality checks, so when the user interacts, the code recomputes the new ScreenConfig (using getRenderer), but only redraws the screen if it differs from the previous. This is much easier and more robust than having to decide for each possible user interaction whether it changes what’s on the screen.

You can get the source from the FrakView darcs repository.

Odzangba Dake: Finally compiled it

2008-05-13T17:04:44+00:00

I finally got some free time over on Sunday to compile the 2.6.25.3 kernel and I was very surprised at how easy it was. I’ve read some ghastly stories about custom kernel compiles going horribly wrong and most of the initial tutorials I read were unnecessarily long but I found an excellent tutorial on the ubuntu forums that makes things simple. The only tedious part was choosing what should be compiled… that was essentially the whole point of compiling the custom kernel but that doesn’t mean I have to like it. It took just about an hour and a half to finish compiling and then I found out I had not enabled CONFIG_TIMER_STATS (powertop needed it to estimate power usage) and I had to do it all over again.

Now that I know how to compile the kernel however, my natural urge to speed things up has taken over and I spent the best part of the night disabling kernel modules and options I did not need. This might occupy my time for the best part of the week.

Kofi Boakye: Linux vrs Windows –My Thoughts

2008-05-03T16:21:56+00:00

Change is good but change is very difficult for the majority of people.
I believe that people who say that linux is not ready or is not as user friendly as Windows are making a mistake.This is simply because Linux is not Windows and may never be Windows.It seems that because these people started their computing life with Windows they seem to think that using Linux should be the same as Windows.Impossible.If possible then I guess there will be no need to have Linux.We will just have Windows and Windows 2 ; the same everywhere.
This “thingy” also seems to be something that affects Linux users also since Linux advocates also tend to badmouth Windows users sometimes very unpleasantly.Please its got to stop!!.
Its quite bad and a sign of intolerance to “diss” someone because they have decided on something or made a choice that you disagree with.Come on !!.VARIETY IS THE SPICE OF LIFE.Imagine how boring it will be if everyone wore the same dress or did the same things.sheesh.
These are two different operating systems with different GUIs or desktops.
Also dont forget despite all supposed bad stuff Microsoft like Linux does employ people who though they may not agree with their employers objectives or mission statement or philosophy,have to earn a living and as such have no alternatives.Also in areas like Africa since most organisations use Windows,it does serve as a means of livelihood for computer technicians with many charging for burning an XP or Vista cd and doing installations of Windows(more on copyright issues and licensing in Ghana,my motherland).

I think the best way to check all this “My own is better” competition will be to get two people with no computing knowledge who will be then introduced to Linux and Windows separately and following each other that is one would start his or her computing life or experience with Windows and another will start with Linux.They will then switch over after some time and share their experiences on each as compared to the operating system they started on.I believe this will then serve as a better means of really evaluating which of the two operating systems is better in terms of user experience or functionality.
Of course the top bleeding edge sample or product of each operating system will have to be used.
Also one must not forget that Linux distros are constantly being tweaked and improved.Its like having a product/research that you cant really finally bring out and say “Aahh!!Finally I’m done.Igor its alive!!!”. Its never ending unlike Windows or Apple where a product is released and left on the market until a new version comes along.
Unfortunately this could also throw a kinda bad light on Linux constantly since improving your stuff means you may decide not make your product better at once and roll out but instead roll it out by degrees and slowly add improvements making the product interesting as you go along.Kinda like a software engineering problem.All of this is IMHO of course with no insult intended to any Linux distro developers.

Funny enough I dont seem to recall a time when people ever argued about or had a war on the merits of Windows vrs Apple or Apple vrs Linux.Why not????

For those who claim that they cant get the look,feel and operation of Windows applications on Linux applications I just want to ask them “have they tried investing a little bit of time and effort into learning and using Linux applications effectively?” Its not as if there was no learning curve associated with learning how to use Windows applications.They definitely had to take some time to learn how to use these software.Reading manuals and so on.So why cant they do the same with Linux software??Especially with the tons of available manuals and tutorials on how to use Linux applications.
For those who also tend put forward the claim that Windows has a larger software base than Linux as their main reason for not fully using Linux I believe that this is no longer so especially with the huge amounts of software found in repositories and being constantly produced.Of course big game companies like EA and so on could also help by writing or porting by cool and fine games over to Linux.
I have an idea that we could something like the DirectX api for Linux.I mean OpenGL and Mesa are there but we need something that is failsafe and guaranteed to make gaming more d**n fine than it is now on Linux.
Of course I have to say that Linux games rock.There are many games for everyone.I’m currently convincing the kids and my parents that Linux rocks for kids due to the number of advanced educational stuff available such as gcompris.

From the above therefore I think that if we want Linux world domination then we have to think about Linux in a different way altogether.
Unforunately I’m still trying to think of how this can be achieved.
Any ideas?????

ABOUT ME:I’m currently a university student studying Accounting and living in Ghana,aka the GH, in West Africa.My main passion has always been computers and science.I’m also crazy about Linux and free and open source software.

Odzangba Dake: Still Here, People!

2008-05-02T16:48:36+00:00

Yeah, my internet access problems have almost melted away so it’s back to business as usual. Which reminds me, I should rant about slow internet here in Ghana one of these days…

Kofi Boakye: I’m baaaaaaaaaaccck

2008-05-01T14:40:32+00:00

Wow! Like the genie stuck in a bottle i’m free at last.
Actually i wasnt stuck anywhere.I just had a long vacation to clear my head and get ready for the new stuff that will hopefully come up this year.
I’m now the proud owner of a MEDION TCM Edition Notebook.YEEEEESSS! Tis like a dream come true.GHz range processor,Lots of harddisk space,cute ,portable and best of all inbuilt wifi.Now i can try some wardriving and get access to free internet in hotspots.With free and hopefully reliable net access(both wifi and wired network) the power of synaptic to me as a user in Ghana becomes realistic and just breathtaking.I mean u can get all of these gazillions of programs free of charge and which are easily installable?? Now thats what i’m talking! On another note i hope someone or an organization in Ghana will offer to do local hosting or mirroring of the ubuntu repositories cuz it really takes some time to download stuff from the rpositories.Anyone???
Since getting this lap i’ve really come to love being able to use my computer anywhere,anytime.Self-Immersive Computing???
Hopefully with the acquisition of this notebook i will be able to resurrect my programming activities.Started sometime ago learning how to code but got bored cuz the machine i had at home just wasnt situated at the right place and was way too uncomfortable to use.Aah !!
Below are some pics of my notebook.Aint she a beaut????All virgin white.!

Henry Addo: The Programming Way Of Proportionally Resizing An Image

2008-04-26T05:55:01+00:00

One of the project I baby sit lately is The Kamusi Project; an online swahili dictionary. One feature we needed on the website was a slide show [ which we use to have before when the project was hosted at yale ] so we can play a slide show of the images submitted by users. [...]

Joachim Breitner: Pausable IO actions for better GUI responsiveness

nomeata — 2008-04-24T22:50:00+00:00

For a university seminar I’m currently writing a GUI program to view fractals based on simple iterated function systems (only similaritudes allowed). It supports three different drawing algorithms and you can edit the IFS by dragging squares around on the screen. But this post is not about this program (I might present it later), but how Haskell allowed me to solve a problem very nicely:

The first instances of the code had a problem that a lot of GUI programmers know: The drawing of the fractal took quite some time, and during that time the gtk main loop is blocked and the program becomes unresponsive. At first I avoided this problem by manually splitting the drawing function (e.g. by repeatedly increasing the resolution) and kept re-drawing it at higher resolutions in an idle handler, so at least I could interact whenever one resolution has finished drawing. It worked somewhat but it was not easily done for the other, not pixel based, algorithms and it was ugly.

So I wanted a way to (a) pause the drawing at any convenient point, to resume it later, and (b) safely abort the drawing if what I’m drawing has changed and I need to restart.

A common solution to this would be to do the drawing in a separate thread, so (a) is actually not needed, but I did not know if I can safely do (b), and I have heard that threads cause problems with gtk.

So I tried to dig deeper for the hidden treasures of advanced haskell programming: I need a monad transformer! I expected the infamous ContT monad transformer to help, but I couldn’t figure out how, and I started to create my own monad transformer, called CoroutineT.

I tried to figure out what an action of type (CoroutineT IO a) should do, and I came up with this type signature:

pausingAction :: IO (Either (CoroutineT IO a) a)

which means that after the pausingAction is done, it is Either paused (and I get back another pausingAction to run when I want it), or it is done (and I get the result). Note that I’m writing IO here, but it can be any monad.

The definition of the datatype and the monad instance came mostly from trying to make this type work (yay to haskell’s type system, less thinking required), and looks like this:

data CoroutineT m a = CoroutineT {unCoroutineT :: (m (Either (CoroutineT m a) a)) }

instance (Monad m) => Monad (CoroutineT m) where
    return v = CoroutineT (return (Right v))
    a >>= b = CoroutineT $ do
          r <- unCoroutineT a
          case r of
            Left  paused   -> return $ Left (paused >>= b)
            Right unpaused -> unCoroutineT (b unpaused)

This translates to english like this: A call to return is not paused. When an action is already paused, further actions should be run after the paused action is resumed. When an action is not paused, further actions can happen now.

Like every well behaving monad transfomer, I also need a "runCoroutineT" function to start the coroutine. I probably could have used unCoroutineT directly, but for my use case (GUI drawing) I did not need a return value, so this function is more handy:

runCoroutineT :: Monad m => CoroutineT m () -> m (Maybe (CoroutineT m ()))
runCoroutineT a = either (Just) (const Nothing) `liftM` unCoroutineT a

Nothing surprising here, basically just turning the Either into a Maybe. So it becomes clear how to do (b): We can just throw away the resume action returned by runCoroutineT (if any). The more interesting thing is how we do (a): We need a pause action of type (Coroutine m ()). But how should it work? I did not really try to understand why it works, but by looking at the types, I came up with this:

pause :: Monad m => CoroutineT m ()
pause = CoroutineT (return (Left (CoroutineT (return (Right ())))))

Yes, it sounds like some dance step instructions (read the second line out aloud!), but it works somehow.

So here is some example code: I have a pausable IO action that counts from one to ten, pausing after each number. I also have function that resumes an pausable action up to n times:

example n = keepGoingFor n $ do
        liftIO $ putStrLn "This is the coroutine"
        forM_ [1..10] $ \i -> do
            liftIO $ putStrLn $ "Counting to "++ show i ++" while you keep calling it"
            pause

  where --keepGoing :: Monad m => CoroutineT m () -> m ()
      keepGoingFor 0 _   = putStrLn "Here I just abort the run"
      keepGoingFor n cor = do
        resume <- runCoroutineT cor
        case resume of
            Just runAgain -> keepGoingFor (n-1) runAgain
            Nothing       -> putStrLn "Finally stopped"

And here is the output of two different runs:

*CouroutineT> example 5
This is the coroutine
Counting to 1 while you keep calling it
Counting to 2 while you keep calling it
Counting to 3 while you keep calling it
Counting to 4 while you keep calling it
Counting to 5 while you keep calling it
Here I just abort the run
*CouroutineT> example 14
This is the coroutine
Counting to 1 while you keep calling it
Counting to 2 while you keep calling it
Counting to 3 while you keep calling it
Counting to 4 while you keep calling it
Counting to 5 while you keep calling it
Counting to 6 while you keep calling it
Counting to 7 while you keep calling it
Counting to 8 while you keep calling it
Counting to 9 while you keep calling it
Counting to 10 while you keep calling it
Finally stopped

So it does really works fine, and it proved very useful in my GUI drawing problem. For that, I created this nice control structure which works like mapM_, but calls pause every n iterations, and therefore hides the pausing stuff almost completely:

pausingForM_ :: Monad m => Int -> [a] -> (a -> CoroutineT m ()) -> CoroutineT m ()
pausingForM_ period list action = pausing' 0 list
  where pausing' _ []     = return ()
        pausing' n (x:xs) = do action x
                       if n==period then pause >> pausing' 0     xs
                                    else          pausing' (n+1) xs

I have put the complete module (including instances omitted here) in the darcs repository that might later also contain the fractal drawing program.

Joachim Breitner: Announcing DarcsWatch

nomeata — 2008-04-17T17:25:15+00:00

A lot of haskell-related projects use the darcs version control system. Darcs has the nice feature that you can easily submit a patch by e-mail, usually sent to the project maintainer or a mailing list. What has bothered me in the past was that I had to manually check whether my patch was applied yet.

So this week, I wrote DarcsWatch. DarcsWatch receives submitted patches and compares them to the repositories it knows about, whether the patch is missing there or not. You either send your patches to DarcsWeb directly when submitting them, using CC, or DarcsWatch is subscribed to the project mailing list itself, which is the case for the darcs-devel and xmonad lists. Other than that, not much is to do, and you’ll find a nice overview of your patches, like this overview of my patches, with diffs and download links.

If you want to use DarcsWatch for your contributions to other projects, or for your own projects, have a look the documentation. There are probably still bugs around, and the problem of marking patches as obsolete is not really solved yet, so if you have ideas about it, mail me, comment here, or come to #darcs on freenode. Patches are always welcome, you can get the source from DarcsWatch’s repository.

Kwasi Kwakwa: Aah, beaten to it(another Wire post)

2008-04-07T11:40:20+00:00

There was meant to be a follow up to my post on The Wire where I would discuss what a version of that show looking at Africa would look like. However I’ve been slow about writing these things and so fellow African geek aflakete pointed me to this post on Brown Man’s Burden that beat me to the punch. Hence I’ll just quote him

I think an interesting show, similar to the Wire, could be made about economic development and foreign aid. It would document NGOs, the World Bank, bureaucrats, politicians, big foundations and academics in their efforts to distribute aid and stimulate economic growth.

The key would be to show how the self-interest of each of these groups both helps and hinders the process of growth, and to convey how complicated stimulating growth and poverty alleviation is.

Obviously the man is a genius since we both had the exact same idea. Except he’s faster at writing these things out than I have been recently. Its still a great idea though, and it’ll provide a convenient launching pad for my next post on this topic. Sooner rather than later people, don’t worry.

Kwasi Kwakwa: Why I will miss The Wire

2008-04-06T21:25:31+00:00

Some of you have heard of The Wire, a crime show that ran for 5 seasons on HBO and recently came to a close. Actually if you are a regular reader you probably have heard of it. I tend to run in those kinds of circles.

For those of you who haven’t heard of it, the link above will cover all the details if you are interested. In short though, it is a show that primarily operates from the point of view of the police and criminals in the city of Baltimore, Maryland and then uses that point of view to examine the cracks in the American dream in its inner cities and former industrial towns in a manner that is nothing short of remarkable. Personally I believe it is one of the best written television shows I have ever seen.

What makes this show great in my eyes, and most likely one of the same things that prevented it from achieving the kind of mass acclaim it deserves, is the way it has continually avoided overly simple and neat explanations of problems in favour of the kind of nuanced view that is rarely see in either real life or fiction.

In their world, there are multiple instances when the question of who is good, who is evil and what actions are appropriate is left to the audience instead of being explicitly spelled out for them to an accompanying soundtrack. Even more impressive though, social problems aren’t solved by 30 second simple fixes that involve one person’s removal or miraculous change of character. Instead we are shown the overlapping circles of dysfunction in the police, the media, the political system, local businesses, the school system and the streets themselves and how each enables and reenforces the other. Most of the people we spend time around are hemmed in my these systems and forced to choose between a series of very limited options, each with its own set of consequences. Some choose well, most choose badly, although again the question of which is the right choice is left to the judgement of the viewer a majority of the time.

For the most part, people who talk about this stuff tend to assume that their audience lacks the attention span necessary to digest a multifaceted view of life and therefore are only capable of dealing in terms of overly simplistic narratives with all the lines clearly sketched in for them and there is no hint of complexity, underlying issues, overlapping causes or anything else that might actually require them to assume the people they are being told about live lives every bit as complicated as theirs, if not more so.

In a lot of ways, The Wire’s insistance on a nuanced look at a world usually dominated by simplistic narratives and a complete lack of empathy reminded me a lot of the larger conversation about Africa. A lot of the time instead of a proper look at the mix of factors that cause things to be the way they are in my part of the world, a simple narrative of ‘vampire states’ or something equally inane to cover a much wider range of issues.

Anyway, that minor rant aside, I’m going to miss this show. It was 5 seasons of memorable characters and the kind of writing that draws you in regardless of whether or not you want to be drawn in.

Joachim Breitner: My stuff on YouTube

nomeata — 2008-04-03T23:57:53+00:00

I usually don’t blog this much, but sometimes it all comes together. And I usually don’t blog about YouTube videos, but this is an exception: Someone put a video there to show off with the pidgin-blinklight plugin I wrote – cool. (The video itself isn’t that cool. But still.)

Joachim Breitner: Distance Map Morpher

nomeata — 2008-04-03T23:30:29+00:00

In my last blog entry, I was asking for algorithms to morph a picture so that contour lines would become circles. I then started to write some python/gtk/cairo code to actually visualize my thought. It came out relatively pretty, so I made the GUI around it usable (although far from nice, I guess) and put the current, early version in a darcs repostory (DarcsWeb browser available).

This is a screenshot (click for full version) of a map of my part of town, shamlessly stolen off the internet. The red shading shows the distance from the thick point of the graph – the redder, the closer. On the right the image is morphed so that all points on a circle around the center have the same distance to it. The blue shape on the left and the blue circle on the right are points with distance 205.

Below the user can

manually select the distance to highlight,
open a new image (with graph and cached calculations along, if present),
save the graph (and the cached calculations),
go to graph editing mode or get a short usage summary of that,
set the offroad penalty,
recalculate the distance function (which can be quite slow ATM),
recalculate the red height map,
set the interpolation method and the zoom level for the morphin,
recalculate the morved image,
or do all recalculations in one step.

Currently, there is one algorithm to determine the distance of a point to the center: Travel along the graph to the most suitable edge, leave at the point closest to the target and then go “crossroads”, which comes at a greater cost.

There are some things to do, most notable:

Faster distance generation, by better graph representation (e.g. so that it’s easier to find the nearest vertex)
Faster drawing
Better, less distorting morph algorithms. Some ideas are in the comments to my previous post.

Comments and patches are, as always, welcome. If you want to try it out make sure you have python2.5, pygtk and numeric-python installed.

Joachim Breitner: How to make contour lines circles?

nomeata — 2008-04-03T08:41:46+00:00

Dear lazyweb, I have a question with regard to image manipulation. Given an rectangle image with a continous function on it (in my case, walking distance from a certain point), I can easily draw the contour lines of the function, i.e. for a given distance from the center mark all points that have this distance. This looks very similar to the contour lines of height map. I’d like to morph this image now that all these contour lines are circles around the centers, but I don’t have a good idea how to do that with a minimum amount of distorting. Any suggestions or pointers to algorithms are welcome.

Kwasi Kwakwa: How did it take me so long to notice this?

2008-03-28T16:04:08+00:00

Proof that I’ve been neglecting my blogroll to a degree, I missed this TED talk.

Its by Dr. Neil Turok, a Physicist at Cambridge and founder of AIMS(African institute of Mathematical Sciences) which is a school in South Africa that brings together students from all over the continent for a 9 month postgraduate course to learn advanced mathematical and computer skills.

The talk is very, very much worth listening to. And I’m wondering if they’ll have use for a certain Ghanaian physicist in a few years time. This is one of those jobs I’d be more than happy to settle into.

Joachim Breitner: The problem with turing complete editors

nomeata — 2008-03-16T22:09:40+00:00

I was just editing a file with vim and was about to do the same few strokes repeatedly. I vaguely remembered something about recording macros, so I tried it: I pressed q-1 to start recording, did my steps (a yank, a movement, an insert, a paste, a movement), and finished the recording with q. Now I could repeat these steps with @-1.

I then noticed that I forgot something at the end (moving the curser to the beginning of the line). I re-started recording (q-1), thought “hey, maybe I can insert the old recording here” and pressed @-1. Surprisingly, that worked. I added the missing movement and finshed the recording with q.

When I then tried to recall these commands with @-1, the editor froze and I was wondering whether the network connection went down (I was working over SSH). But it wasn’t, and it dawned me that vim did not insert my old commands when re-recording the macro, but just inserted the call to the macro itself. My text editor was caught in a infinite loop...

Not too bad, I just killed vim, did not lose anything and everything was fine. But I think an editor, even vim, should somehow prevent such behaviour.

Odzangba Dake: Compiling A Custom Kernel…

2008-03-11T19:54:54+00:00

I finally got around to downloading and compiling powertop this afternoon but unfortunately, I couldn’t use it since my kernel was just too old (2.6.20-16) and it wanted 2.6.21 and higher. I’ve stuck to this particular kernel (and feisty for that matter) because I only have mirrors for feisty. Internet here in Ghana is usually crappy so until I get the gutsy (or hardy, when it finally gets released) mirror, I’m sticking with safe-and-convenient.

But I digress… I grabbed the 2.6.24.3 kernel and now I’m scouting around on the net for potential issues arising from compiling that kernel version on my hardware. It’ll probably take me another hour or so to make sure all is good (or at least can be made good with a few fixes), write out my will, say my last prayers and then I might probably be just in the right frame of mind to compile the kernel, I think… maybe.

I’ll post the details later…

Joachim Breitner: Creative Week of Snowboarding

nomeata — 2008-03-03T22:59:39+00:00

I was snowboarding with some friends last week, and in the evenings I had a little rush of uncontrolled creativity: I wrote a new entry in my (German) tech parody news about guitar hero in music education and two new parody songs: “Pain of Boarding” instead of “Sound of silence” and a snowboard-variant of “I will survive”. I’ve also hacked up my XML/XSLT/make-website-system to include the songs, so you can find all my songs there now as well.

Odzangba Dake: Flirting With Miro Internet TV Player

2008-02-28T18:31:15+00:00

Ever since Akuafo Hall opened up its own ICT centre, I’ve been spending more time on the internet, largely due to the fact that laptops are allowed. Anyways, one of the apps I’ve been trying out it Miro. I’ve played it before when it was going by the name Democracy Player but did not have much use for it since I had such horrible internet. But I pulled it from Canonical’s commercial repository this afternoon and I’ve been loving every minute of it. The interface is very clean and without any screen clutter and it’s terribly easy to use. I’ve a few screenshots to show for my afternoon’s adventure.

Kwasi Kwakwa: the story so far…….

2008-02-25T20:45:48+00:00

As usual, there has been a bit of a time lag in my blogging. I’m working on getting more regular at this people. Until then please forgive the absences. I assure you I am actually working (most of)the time I am not here.

Anyway, as far as school goes. I am almost done with the lectures segment of my course. Although to, be honest, their idea of lectures has mainly involved getting us to read and figure out stuff on our own as much as possible and get back to them when extra direction is needed. My research project has been picked though, so I shall be working on nothing else from about the end of march until the end of September when I turn in and defend my thesis.

As for what its about, well, I shall be using the finite difference time domain method to determine the electromagnetic field distribution in the vicinity of silver and gold nanoparticles and find the localized surface plasmon resonances of a range of nanostructures(copied almost directly from the proposal I was given. The links will help explain it but basically I shall be using a FORTRAN program developed as someone’s Phd to run some simulations. I may end up making some modifications to the code too, depending on how things go.

As for Judo, I went for my first competition this weekend At the University of Sheffield International Student Teams competition. The ‘A’ team from my club came in second and our women won the drinking challenge later that night. I didn’t do so well. I fought in the ‘C’ team in the weight class above mine against predominantly better competition. And I made some mistakes I shouldn’t have. Hence I got, thrashed. Still, I have a feeling I shall not be repeating those mistakes again. And, barring any surprise schoolwork, I’ll be fighting in another competition this weekend at my proper weight class against less seasoned opposition. I’ll let you know how that goes. And hopefully I’ll have pictures.

Until then people………….

Odzangba Dake: Unlocking LG DM150 CDMA Phone

2008-02-25T19:51:24+00:00

I took out my LG DM150 phone to make a call yesterday and it prompted me for a four-digit unlock code. So I looked it up in the manual and it said to enter 0000 … didn’t work. So I turned to Google and guess what, my friend Henry had a page on unlocking the same phone. It’s very simple really… just enter the last four digits of your phone number. Though I live in Ghana and use the kasapa mobile network, its appears it doesn’t matter what your carrier is or what country you live in. In my case, I had to enter 8690 since my cell phone number is 028 731 8690.

All the other methods (enter 0000, 1111 or 1234) did not work for me so I really recommend the enter-the-last-four-digits-of-your-phone-number method.

Odzangba Dake: After a long hiatus…

2008-02-18T10:57:18+00:00

Yeah, I’m still alive… just having some internet access problems. Things are getting back to normal now so welcome to a new year.

Henry Addo: Why Vista Sucks

2008-02-18T01:58:44+00:00

Yes this video tells it all. Now after watching that clip consider yourself convinced that Vista sucks big time and also understand why people keep downgrading after few hours interaction with Vista. Yay Vista sucks!!! period. microsoft, vista, windows, xpShare This

Joachim Breitner: Ways to fork privately

nomeata — 2008-02-11T22:49:00+00:00

A few days ago, I asked how to fork a debian package privately. I got some repsonses by comments, e-Mail and other blog posts, and I want to summarize the tools that were suggested. I have not really tried them, just looked at the webpages, the documentation or the sourcecode. I’m only including Debian-specific solutions, as using Gentoo might be nice, but is out of scope here :-)

I also deleted half the text before saving it, and I hate rewriting stuff, so it might be a bit terse.

debtoo

Eddy Petrișor tells me about his three year old project debtoo, which wants to bring a Gentoo-like experience to Debian. While it probably provides what I need, it feels “too big” in that it has a more general aim than what I’m looking for. It is not in Debian and not actively developed in the last two years.

srcinst

Eddy also tells me about srcinst, which is a small haskell program written by jgoerzen in 2005. This is more a proof-of-concept that builds a package and all necessariy build-dependencies without using a binary package, but does not allow for patches to be applied. It is in Debian, actively maintained, but not developed, and barely documented (just an IRC log).

apt-build

A similar tool and also in Debian is apt-build. This package is created to compile packages for optimization (as it asks half a dozend compiler-flag-questions with DebConf during the installation). It allows the user to apply a patch to the source, but it has to be passed as a command line option, and patches seem not to be tracked. Not much development in the last year, and not much documentation.

debpatch

Not to be confused with the program in the debdelta package is the debpatch tool by Victor Hsieh which Carsten Hey told me about. Also written in 2005, this comes closest to what I want. For every package you want to modify, you can configure it to apply patches to the source, to add patches to the debian/patches directory or to statically replace files in the generated binary and puts it in a local apt repository. No code yet to track new versions of the packages and no support for pbuilder though. This perl script is not yet in Debian, but is available as a Debian package and seems to have seen some development in the last years. Quick Googleing does not return any user reports; has any already tried this?

customdeb

Somewhat in this direction goes the script that I wrote two weeks ago for a totally different project, customdeb, but it is aimed at binary debian files exclusively, and debpatch already supports replacing files in the binary package.

apt-src

Also a related tool Carsten Hey told me about is apt-src. This tool wants to provide apt-like features for source packages. It allows you to “install” sources somewhere, upgrade the source and build binary packages from them. It does not really hide the sources from the user and seems to be created for people who want to work with the source somehow. If you have local changes to the sources, it can try to merge them with the new version, but these changes are not kept as a separate patch but only as implicit changes. If that were different, it would seem be a very nice tool. It’s written by Joey Hess he abondonned it in 2004. Since then, not much development has happened.

debnest

Yet another approach is taken by debnest, which Peter Makholm took over. Here, you create a full debian source package with a debian/ directory containing a control and rule file etc., but besides the debian/ directory, it contains just the packed sources (.dsc et al) from another package. In your debian/rules, you can specify your changes. I can see no support for tracking new versions of the inner package, but at least this project is maintained and in Debian.

Summary

I found a few projects that go in a similar direction, and one that seems to fit my needs quite well. All of them are not widely used and in a very early state of development, and it seems to be something people start to work on and quickly lose interest. I’m actually surprised that this is not a itch more people had to scratch! I will have a closer look at debpatch when I find the time and maybe, if found useful, see if it can be included in Debian − probably after a name change, since we already have a debpatch binary. Or maybe I should try to add support for what I need to apt-src, which seems to be the most advanced of all these programs, although it’s unmaintained longer than the others exist.

Update: Added apt-src.

Update 2: Added debnest;