## Archive for the ‘Technical’ Category

### Adding local latex packages to texlive in ubuntu

February 19, 2011

### Two Columned LaTeX Presentation Slides

December 7, 2009

Coming from a Power Point background of creating presentation slides, i am often tempted to used a two column approach when laying out the content of my slides. This is where text is shown on the left column and related pictures are placed on the right.

After i decided to to move all my document creation work to be in LaTeX, I started to also create my presentations that way too. Such a feat is made possible using the beamer document class, whose user guide could be found here.

The environment for a single slide is the “frame” environment. It is used a follows:

\begin{frame}{frame title}

\end{frame}

To be able to split the frame (slide) into two columns, the “columns” environment is places inside the slide content. It is used as follows:

\begin{columns}
\column{column_width} %first column
column 1 content
\column{column_width} %second column
column 2 content
\column{column_width} %third column
column 3 content
...

It is best to have the column_width in terms of the text width. So for example:

\column{0.5\textwidth} %half slide's text width

An example for a two columned slide looks as like:

\documentclass{beamer}
\mode<presentation>
{
\usetheme[width=2cm]{Hannover}
\setbeamercovered{transparent}
}
\title[Presentation]{Presentation}
\author[Saher Mohamed El-Neklawy]{Saher Mohamed El-Neklawy}

\begin{document}
\begin{frame}{Frame Title}
\begin{columns}
\column{0.5\textwidth}
\begin{itemize}
\item Item 1
\item Item 2
\item Item 3
\end{itemize}
\column{0.5\textwidth}
\includegraphics[width=\textwidth]{i1.eps}

\includegraphics[width=\textwidth]{i2.eps}
\end{columns}
\end{frame}
\end{document}

Two Columned Slide

The next step is to sequence the appearance of the images along with the images. In the beamer class, this could be done using the “” operator, following a certain component in the frame. The “n” represents when the component appears in the frame. For example:

\begin{itemize}
\item<2> Item 1 % seen after 1 transition
\item<3> Item 2 % seen after 2 transition
\item<4> Item 3 % seen after 3 transition
\end{itemize}

In a sense, the “” splits a frame into n slides, placing the respective component in the nth slide of that frame. For more advanced uses of “”, check out the beamer class user guide.

To do the same for images, the “\visible” or “\only” macros could be used along with the “” operator.

With using “\visible”, the slides would now look like:

\documentclass{beamer}
\mode<presentation>
{
\usetheme[width=2cm]{Hannover}
\setbeamercovered{transparent}
}
\title[Presentation]{Presentation}
\author[Saher Mohamed El-Neklawy]{Saher Mohamed El-Neklawy}

\begin{document}
\begin{frame}{Frame Title}
\begin{columns}
\column{0.5\textwidth}
\begin{itemize}
\item<2> Item 1
\item<3> Item 2
\item<4> Item 3
\end{itemize}
\column{0.5\textwidth}
\visible<2>
{
\includegraphics[width=\textwidth]{i1.eps}
}
\visible<3>{
\includegraphics[width=\textwidth]{i2.eps}
}
\end{columns}
\end{frame}
\end{document}

Sequenced Two Columned 1

Sequenced Two Columned 2

The problem with “\visible” is that it keeps the place of the component from the previous transition reserved in the next, just not seen. The fix to this issue is the use of “\only”, where the space for components is not reserved across transitions. Such makes the slides look as follows:

\documentclass{beamer}
\mode<presentation>
{
\usetheme[width=2cm]{Hannover}
\setbeamercovered{transparent}
}
\title[Presentation]{Presentation}
\author[Saher Mohamed El-Neklawy]{Saher Mohamed El-Neklawy}

\begin{document}
\begin{frame}{Frame Title}
\begin{columns}
\column{0.5\textwidth}
\begin{itemize}
\item<2> Item 1
\item<3> Item 2
\item<4> Item 3
\end{itemize}
\column{0.5\textwidth}
\only<2>
{
\includegraphics[width=\textwidth]{i1.eps}
}
\only<3>{
\includegraphics[width=\textwidth]{i2.eps}
}
\end{columns}
\end{frame}
\end{document}

Two column slide using only macro 1

Two column slide using only macro 2

When taking a closer look at the output pdf, it will be observed that there is a slight change in the position of the bulleted list. This is most seen between pages 3 and 4 of the pdf. Such is due to the nature of the \only, as it does not reserver the position of component across transitions of the frame. Thus, the location of the bulleted list differs when there is a transition with a slide having a slide to one without, and vice versa.

This problem could be fixed by going back to the “\visible” macro, as it reserves the spaces for components. The difference this time is is that the location of the image in the slide will be forced. This could be done using the “picture” environment as follows:

\begin{picture}(0,0)(x,y)
\put(0,0){\includegraphics[width=\textwidth]{i1.eps}}
\end{picture}

Take care to consider the x and y values from the top right corner of the column.

The final code results in this pdf, and looks like follows:

\documentclass{beamer}
\mode<presentation>
{
\usetheme[width=2cm]{Hannover}
\setbeamercovered{transparent}
}
\title[Presentation]{Presentation}
\author[Saher Mohamed El-Neklawy]{Saher Mohamed El-Neklawy}

\begin{document}
\begin{frame}{Frame Title}
\begin{columns}
\column{0.5\textwidth}
\begin{itemize}
\item<2> Item 1
\item<3> Item 2
\item<4> Item 3
\end{itemize}
\column{0.5\textwidth}
\visible<2>
{
\begin{picture}(0,0)(40,50)
\put(0,0){\includegraphics[width=\textwidth]{i1.eps}}
\end{picture}
}
\visible<3>
{
\begin{picture}(0,0)(50,50)
\put(0,0){\includegraphics[width=\textwidth]{i2.eps}}
\end{picture}
}
\end{columns}
\end{frame}
\end{document}

November 4, 2009

Launchpad is a software collaboration platform developed by Canonical (famous for Ubuntu :D). Recently the the launchpad project went open source. This allowed people to host copies of it locally. The process for the installation process could be found here.

The next natural step is to configure remote computers to be able to access launchpad. After following the how-to by launchpad, and trying the access the local copy of launchpad from an external source, the following error is shown by the running launchpad server:

object at 0x8157b50>, name: ''

The solution to this lies in the /etc/hosts file on the client accessing the lauchpad copy. The file should contain the following:

{ip of the server} is the ip of the machine containing the running copy of the launchpad server. Also take care the lines starting with {ip of the server} until an empty line should be a single line in the file. For client systems that are not linux, check out the Wikipedia article concerning hosts for the files equivalent to “/etc/hosts”.

On a side note, when installing launchpad, it does not add scripts for running automatically at startup, this process has to be done manually.

### Searching Source Code: LXR and grep

November 2, 2009

Looking for a certain functionality in someone else’s code could prove to be a tough challenge. This is increased by the size of the given project. Many systems exist today facilitating easy search in a project. For Java, eclipse is best used for that task, as it contains a strong in java class indexing, classification, and searching.

Some projects provide for you a portal to search their code base. Famous examples of these are LXR for the Linux kernel, and it’s customized version MXR used for Mozilla projects.

When all the above options are not available, the alternative exists natively in most linux systems. This is namely “grep”. Grep is a strong command for regular expression matching. On if it’s features is that it can also match to the content within files. Putting that in mind, the following command could be very useful:

grep -R "search query" .

This looks recursively for all mentions of search query in all files under the current directory. This prints output in the console the file name where this query was found, and the line that included it.

To be able to store this search result in a file, the output could be piped as follows:

grep -R "search query" . > log.txt

### Converting System::String to char *

October 31, 2009

The official way to convert a visual c++ System::String to a char * could be found here. Such strings are everywhere in windows forms applications.

A simpler way (for people who are used to using standard c\c++) to do the conversion is as follows:

void string2charPtr(String ^orig, char *&out)
{
int length = orig->Length;
out = new char[length+1];
for(int i=0;i<length;i++)
out[i] = (char) orig[i];
out[length] = '';
}

Please feel free to comment on the function above.

### Processing.js:Reinventing the wheel

October 26, 2009

HTML5 is the new standard for web pages. One of the most exciting features that it introduces is the canvas tag. This component allows rendering vector graphics on the browser. This was not previously possible with older HTML versions.

With that advancement in HTML, new JavaScript libraries emerge to be able to create vector visualizations at the client side. One of these libraries is Processing.js, which is a port of the java processing library.

For a first look at processing, the examples show very exciting examples. But the week point of the framework shows when try to develop an application that required much interaction week. To reach such an application, the “processing.js” written has to be highly optimized. No room for unnecessary code execution, use of floats or doubles, cache as much as you can, etc….

My other issue with Processing.js is the fact that they ported from the java library everything, even the syntax. This comes to be very frustrating to web developers. The first reason for that is most web developers are used to the syntax of JavaScript, so having things like int x=0; and int [] arr = new int[4]; come as a big surprise. This could be good for the java developer, but not the the web developer.

My other bone to pick with Processing.js is how primitive it is relative to the current state of the web. There are no components, and you can’t define events on specific components. Everything  has to be done from scratch. Further strengthening the point of needing highly optimized code.

Backing to the title of my post, Processing.js tries to provide an alternative for Flash. In the web, the major disadvantage of Flash is it’s isolation from the rest of the webpage, making it an independent entity. Processing.js does not over come this problem, as the visualization code for each canvas is a world of it’s own. It can only access normal JavaScript code in the same page (which is possible with ActionScript 3’s ExternalInterface). This problem even escalates with lack of direct communication between different canvases directly using Processing.js code. Furthermore, Flash is currently cross browser compatible, unlike the canvas tag due to it’s new addition to the HTML standard.

Putting all the above factors in mind, I feel that using a the much mature flash plugin libraries which are closer to web developers is the best option currently in the market until the canvas tag matures more with richer libraries.

### Finding your true computer name on the network

October 13, 2009

In many cases, it is essential to find the name of a computer over a local network. Such fits well when on a DHCP network, and need to always reach a certain machine.

An easy way to obtain this data, is via the python socket library. The ip of the desired machine is obtained via ipconfig (windows) or ifconfig (linux). For the sake of the example, assume that the ip from the DHCP network is 10.0.0.5.

In the python interpretor, execute the following code:

import socket