The Hackish Blog

Cake Pattern: Much more than just Dependency Injection

2012-06-19T21:47:00.001-04:00

When you search around for dependency injection (DI) in scala, you will find the dominance of the "Cake Pattern". "Cake Pattern" is Scala's answer for dependency injection (DI) using language's built-in features. It has two widely advertised advantages: (1) You have dependencies statically linked, and (2) there is no need for external libraries. Nice, eh?

But, there is a small unique feature that makes the cake pattern much better than any DI tool around (well, the one I know of). And what's that feature? I don't have a name for it, but I can explain it through an oversimplified example (inspired from a true story).

Suppose that you are developing a web framework and you need to compile your javascript using a javascript compiler (say Google Closure) for each page. Imitating other DI tools, you probably would develop something like this:

Loading ....

In words, this code is similar to "give me the compiler" and then "hey compiler! compile these javascript files for me". But, all page renderers will have a set of files to compile, and a similar call to the compiler: {compiler.compile(jsFiles)}

In real world, this simple call to the compiler sometimes involves several steps; a source of boilerplate.
Instead, if we enforce the PageRenderers to specify their javascript files, we can reduce the boilerplate to:

Loading ....

In words, this code is similar to "I have some JS resources" and "I need them compiled!". In other words, in the first snippet, the page render push to the compiler, and in the second snippet, the compiler pulls from the code. When you have quite a few dependencies for a class (say, a soy compiler, a css compiler, a closure compiler, and some DAO), pull-based DI would have much less boilerplate.

To the best of my knowledge, you can't do this using other dependency injection tool (including Guice). The Cake Pattern has a notion of "injected inheritance" (here you go! I just invented a name), and I really liked it.
Google+ Page

Solving NOX Tutorial and Twisted 10.1+ Problem

2011-11-30T14:49:00.001-05:00

Trying to run NOX (specially the nox-tutorial branch; the one installed by mininet) on an updated distro, you probably get the following error:
00001|nox|INFO:Starting nox_core (..../noxcore/build/src/.libs/lt-nox_core)
00002|nox|ERR:Cannot change the state of 'python' to INSTALLED:
'python' ran into an error:
Unable to construct a Python component:
Traceback (most recent call last):
File "./nox/coreapps/pyrt/pyoxidereactor.py", line 364, in instance
return pyoxidereactor(ctxt)
File "./nox/coreapps/pyrt/pyoxidereactor.py", line 133, in __init__
signal.signal(signal.SIGCHLD, self._handleSigchld)
AttributeError: 'pyoxidereactor' object has no attribute '_handleSigchld'

I have tried different ways to resolve this issue, but only 1 of them works: Replace your twisted-10.1+ with twisted-10.0.

Remove your intalled twisted:

sudo apt-get purge python-twisted

Download http://twistedmatrix.com/Releases/Twisted/10.0/Twisted-10.0.0.tar.bz2 and uncompress it.
Install it using setuptools:

sudo python setup.py install

Unity Sucks

2011-06-03T13:37:00.000-04:00

Unity, as released in the Ubuntu 11.04, sucks IMO. It is an unstable, naive, inconsistent, temperamental, yawn-pingish Mac mimic! Let me just briefly point out the very annoying problems of Unity:

Unity search does not support short cuts! Try copy/paste something to the search bar! Funny, isn't it?
There is no way to clear history from the UI! You have to clear it on terminal: http://www.webupd8.org/2010/12/how-to-clear-zeitgeist-history-quick.html
You cannot launch a new instance of a running application! OMG!
The new mimicked vertical tiling, and full-screen apps is just a hack!

Being a Mac is not just imitating its functionality. Switch to Gnome Shell and make it stable, useful, innovative, consistent, and permanent.

Upgrading to Xen 4.0.1 on Ubuntu 10.04.1 x86_64

2010-12-15T14:56:00.000-05:00

I have been wrestling with Xen 4.0.1 to make it work on my machine with Ubuntu 10.04 (64 bits) for two hours, and finally I pin it to the mat.

There is a nice guide for installing Xen 4.0.1 on Lucid and it works fine unless you have an ATI graphic card driven by the proprietary driver :(.

So, before booting your XenoLinux, you have to disable to the open source driver if you're using ATI's X11 driver. Secondly, add nomodeset to the boot options:


menuentry 'Xen 4 / Ubuntu, with Linux 2.6.32-26-xen' {
    recordfail
    insmod ext2
    set root='(hd0,1)'
    multiboot (hd0,1)/boot/xen.gz dummy=dummy dom0_mem=1024M
    module (hd0,1)/boot/vmlinuz-2.6.32.26-xen dummy=dummy nopat root=/dev/sda1 nomodeset earlyprintk=xen ro 
    module (hd0,1)/boot/initrd.img-2.6.32.26-xen
}
menuentry 'Xen 4 / Ubuntu, with Linux 2.6.32-26-xen (Recovery mode)' {
    recordfail
    insmod ext2
    set root='(hd0,1)'
    multiboot (hd0,1)/boot/xen.gz dummy=dummy dom0_mem=1024M
    module (hd0,1)/boot/vmlinuz-2.6.32.26-xen dummy=dummy nopat root=/dev/sda1 nomodeset earlyprintk=xen ro single 
    module (hd0,1)/boot/initrd.img-2.6.32.26-xen
}

And then just boot it.

Ubuntu must-add #1

2010-12-02T11:01:00.000-05:00

SSH client on Ubuntu is not configured to prevent SSH connection timeout on idle sessions. I always had this problem on my Ubuntu machines and Idle connections were closed too soon. You can fix this problem by a simple change in your SSH client configuration file (/etc/ssh/ssh_config):

Host *

ServerAliveInterval 200

It will send the server an Im-alive packet each 200 sec. It will keep your ssh connection ALIVE!

(c) http://embraceubuntu.com/2006/02/03/keeping-ssh-sessions-alive/

Google TV is out there!

2010-10-25T13:57:00.000-04:00

Google TV is out. Sony and Logitech are the first companies to present it!

I hope there would be some free channels inside! :D

Right to Left and Google Instant

2010-10-23T17:26:00.001-04:00

I tried googling a Persian text in Google, and found something really funny. The shadow auto-completed text cannot be considered as an auto-completion. The input box should be made right to left upon receiving a Persian character just like what YouTube has achieved.

Full Screen Flash on my Secondary Monitor in Linux

2010-10-23T10:45:00.000-04:00

There is a well-known problem for playing full screen flash on the secondary monitor, but dudes have solved it for windows: http://www.lifehacker.com.au/2010/06/keep-flash-10-1-in-full-screen-on-a-second-monitor/

There is no similar approach for fixing the problem on Linux. I got an naive workaround that works for me. I just zoom-in the browser content so the flash width and height becomes as large as a full screen flash. I am now watching my favorite online stream on my TV through my Ubuntu 10.04 and I am really happy with it.

FaceBook Anti Filter 1.3

2009-05-24T14:46:00.000-04:00

The new release contains a preference pane that you can use to change the by pass method.

After installing it from one the following links (Oh my God! Some ISPs have cached the following links you have to wait a day or so to update you plugin):

and restarting you firefox. You can go to the Tools/Add-ons menu. You will see a menu as shown below.

Now click on the option button or the preferences button. Now you see a combo box that you can change to select by pass method.

new.facebook.com is now the default url for the plugin.
https is the method that redirects you on https
You can type any other urls (e.g. www.www.facebook.com) to replace facebook.com url.

Just for fun: type google.com there! :D

BWT, if it does not work out of the box you should you https as by pass method.

Update: This plugin has not been working in Iran for 3 month, because all the facebook ip address are block on the network level.

FaceBook Anti Filter

2009-05-23T13:31:00.000-04:00

Facebook has been filtered in Iran. You can use https:// for loggin on to facebook but you may got some errors sometimes!

I have created a Firefox extension that you can install it from

For newbies:

You need firefox 3.0+. You can download it at http://www.mozilla.com/en-US/firefox/firefox.html
Wait for a counter before installation.
Please restart your firefox to enable this feature!

Update: Now works with the beta versions 3.5b ...

Update: Version 1.1 released. Update your plugin.
Update: Version 1.2 released. Now you can play mafia on facebook.com!
Update: The add-on can be downloaded from Mozilla Addons.

A Persian Java Code

2009-05-17T16:06:00.000-04:00

Copy and paste the class below and just change you eclipse encoding (Prefernces/General/Workspace/Text File Encoding) to UTF8.

public class تست {

int عدد = 0;

public int عددرازیادکن(){

return عدد++;

}

public static void main(String[] args) {

new تست().عددرازیادکن();

}

Making TeXMaker Bidi enabled!

2008-11-21T09:09:00.000-05:00

I was writing my PhD proposal, and using Arabi LaTeX module.

The major problem was that the TeXMaker (my favorite LaTeX editor) does not support right to left texts like the FarsiTeX editor.

I have created a patch based on the 1.8 version of the TeXMaker.

You can download the original source code from http://www.xm1math.net/texmaker/download.html#source and also you can download the patch from http://ce.sharif.edu/~hassas/RTL-for-texmaker-1.8.patch.

The RTL/LTR are available under the Edit menu.

Enjoy the patch!

I'm a programming language GEEK!

2008-08-21T11:10:00.000-04:00

Moslem Habibi has sent me this test and
I got the score below!

Created by OnePlusYou

Persian in TeX

2008-04-10T13:43:00.000-04:00

I finally found a great tool named Arabi TeX for using to create Persian TeX files in LaTeX2e.

This is a sample

arabisample.pdf

arabisample.tex.zip

UPDATE: Thanks Dr. Ghodsi, the problem of the TeX sample on windows is now solved.

Google quote about TCI.ir and irantelecom.ir

2008-02-14T01:57:00.001-05:00

Googling for Iran ITC Ministry web site, I found that the official sites are said to be malware:
http://www.google.com/search?hl=en&client=safari&rls=en-us&q=tci.ir&btnG=Search

It is interesting that TCI can harm my computer!

How geek are you?

2008-01-19T10:56:00.000-05:00

63% Geek

60%

Swapping two integers in Java

2007-12-03T09:18:00.000-05:00

Some of my Java students asked me about how to swap two integers using java in a way like what we have done before in C.

I could not say anything that time, but today I got an idea and solve the problem easily.

The following code is in response to ones arguing that C# is better than Java because it can swap two numbers!
The following code can also be used under GNU Public License v3 (http://gplv3.fsf.org/)

import java.lang.reflect.Field;

/**
*
* @author Soheil Hassas Yeganeh
* This class swaps the values stored in two Integer objects.
* Published under GPLv3.
*/
public class Swapper {
public static void swap(Integer i, Integer j) {
try{
Integer lastJ = new Integer(j);
Field value = Integer.class.getDeclaredField("value");
value.setAccessible(true);
value.set(j, i);
value.set(i, lastJ);
value.setAccessible(false);
}catch(Exception e){
e.printStackTrace();
}
}
public static void main(String [] args){
Integer i = 20;
Integer j = 30;
swap(i,j);
System.out.println(" i is : " + i + " j is : " + j);
}
}

Slow startup/login in leopard solution!

2007-11-15T08:01:00.000-05:00

The first time I installed leopard (Mac OS 10.5) on my MacBook using erase and install option, the startup time was very good about (30 seconds).
I also login almost spontaneously (in about 2 seconds).

But, after when copied about 20 GB of documents, and installed 30 GB of applications, the boot time increases so much.
It took about 20 seconds!
I got that the long boot time was caused by indexing done by spotlight. After some hours putting my MacBook alone and let the leopard index all of my documents, the login time became spontaneously again.

But, some weeks after the login time increased and took about 30 seconds. I wondered why login time was increased.
This time the problem was caused by the caches. I removed all the stuffs in the ~/Library/Caches (where ~ means my home folder), and reboot using Option+Command+P+R. I login spontaneously, after.

That seems great! Clean the caches and preset the options will decrease your login time in leopard.

Make your Eclipse fonts bigger on Mac OS X

2007-05-08T03:30:00.000-04:00

The first time I installed eclipse on my MacBook, I found the default font size of the eclipse, too small.

So I have searched through other blogs to find a solution for this. Unfortunatelly I did not found anything.
Yesterday, when I was editing my eclipse.ini I found the problematic option in my eclipse.ini that makes the fonts of the Eclipse small:

-Dorg.eclipse.swt.internal.carbon.smallFonts

So if you have the same problem as me you can edit $ECLIPSE_HOME/Eclipse.app/Contents/MacOS/eclipse.ini and remove the line of the mentioned option.

Oh no! The daemon is late.

2004-10-01T11:04:00.000-04:00

About 16 days delay!
FreeBSD 5.3-Release was scheduled for October 1st, but now, they will release it on October 17th. What a hard release! Have many works to do.

But, the daemon will serve the best, after release! ( 1MPPS forwarding rate is great on PC, as far as penguin is forwarding about 100KPPS. )
Wish them success!

Starting

2004-09-25T16:06:00.000-04:00

Today, I've found that the only way I can memorize my experiences is Bloggin.
So I've started.