Rev2K

How to learn a new programing language

2010-03-31T14:48:00.000+01:00

When learning a new computer language I usually start by implementing some simple problems. This method helps me get comfortable with the language progressively and quickly.
This is a learn by doing method. So you'll have to get your hands dirty. It's easy to find the code for the problems in the web, but that won't make you a better programmer. You'll have to put your neurons to works and read the language documentation and make a lot of mistakes so you don't repeat them in the future.
The first of this problems is know by all computer developers (I hope).

HelloWorld - compiler/interpreter, documentation - This problem won't make you proficient in the language, but after you finish it you will have a development environment and know how to create a program, compile and execute it. Additionally you will know where to find the language documentation.

PrimeNumer - syntax, loops, maths, logic - The big objective of this problem is to make you aware of the syntax of the language. After solving this problem you will be able to read most of the code written in this language.

QuickSort - more syntax, recursion, lists/arrays - This problem introduces you to richer data types of the language and by now the syntax should be very familiar.

HuffmanTree - stream reading/writing, types/classes - You learn how to think in the language. The language paradigms should be clear now. You are ready to start to solve real-world problems.

The next step is to get connected with the language community and use what you learn in the best way you can.
Sometimes you may find out that the language you just learn is not your cup of tee. But you probably discover something in that language that you can use to improve your programming skill in your language of choice.

My learning method is more oriented to general propose languages like Java, C/C++, Haskell, Python, Ruby, etc...
But I think this method can be successfully used in languages with a more specific scope like JavaScript, Erlang, PHP, Lua, Prolog, Bash and others. Most of these languages can be as generalist as the ones in the first group.

Drawing with openGL on Cocos2d-iphone

2010-03-25T10:33:00.002Z

After a long search in the web, forums, IRC chats and several hours of trial and error... I finally can make some openGL drawing inside cocos2d-iphone objects.
I'm using the version 0.99.1 of cocos2d-iphone.
In the beginning the code was breaking in the call to glDrawArrays() with a EXC_BAD_ACCESS exception. Then I was able to draw a line but there was no color.
To save some time to the ones that were having the same problem here goes my solution.
I created a very simple class that draws colored line.
The class declaration is minimal:


@interface Line : CCNode
{
}

@end

It just has to subclass the CCNode class from cocos2d-iphone.
For the implementation I just had to overload the draw() method.


@implementation Line

-(void) draw
{
static const GLfloat vertices[] =
{
0.0, 0.0,
250.0, 280.0
};
static const GLubyte squareColors[] = {
255, 0,   0, 255,
0, 0, 255, 255
};

glDisable(GL_TEXTURE_2D);
BOOL colorArrayEnabled = glIsEnabled(GL_COLOR_ARRAY);
if (!colorArrayEnabled) {
glEnableClientState(GL_COLOR_ARRAY);
}

BOOL vertexArrayEnabled = glIsEnabled(GL_VERTEX_ARRAY);
if (!vertexArrayEnabled) {
glEnableClientState(GL_VERTEX_ARRAY);
}

glLineWidth(2.0f);
glColorPointer(4, GL_UNSIGNED_BYTE, 0, squareColors);
glVertexPointer(2, GL_FLOAT, 0, vertices);
glDrawArrays(GL_LINES, 0, 2);

if (!vertexArrayEnabled) {
glDisableClientState(GL_VERTEX_ARRAY);
}

if (!colorArrayEnabled) {
glDisableClientState(GL_COLOR_ARRAY);
}
glEnable(GL_TEXTURE_2D);
}

@end

The important parts are that you have to disable GL_TEXTURE_2D and you need to use both color and vertex arrays to do the drawing.
I found out in a forum that having GL_TEXTURE_2D enabled won't allow you to make any drawing with openGL primitives.
Then I was using just vertex arrays with a call to glColor4f(), but this result in a line with no color.

This class is very simple to change so that you can specify the star and end point of the line and the color when you initialize the object.
I hope this will save you some hours of work.

Pimping my Xcode (disable anti-aliasing)

2010-03-18T11:26:00.000Z

Reading text from a screen several hours a day can be very tiring for one eyes. But there is one setting that can make it easier for your eyes. That is font anti-aliasing. It should be disabled.
The anti-aliasing makes the text look prettier but less sharper and consequently it becomes harder to read.
Several text editor for programmers (jedit, bbedit, ...) already have an option to enable/disable text anti-aliasing. Unfortunately Xcode doesn't have a simple way to disable this. You will have to go to the console and type:


defaults write com.apple.xcode AppleAntiAliasingThreshold 18

Now every font under 18 size will not be anti-aliased. But there is another catch. The default font Menlo will look blurry in any size. I chose to use the Andale Mono with a size of 12.

Hope that this help you keep your eyes save.

XCode, macports and SDL ... what a hell

2009-12-21T21:33:00.001Z

After long searches on the web, mailing lists, forums and wikis, I finally got xcode 3.2 compiling/linking my application that uses libsdl.

Using the macports libsdl won't work. Trying to make it work was my big mistake. I was getting compiler errors and linker undefined symbols like "_SDL_PushEvent" and others similar.

The solution was to download all the latest dmg files from http://www.libsdl.org and don't forget the SDL-devel-1.2.14-extras.dmg with the xcode project templates.

Copy all the frameworks (SDL, SDL_Image, SDL_Mixer ...) to "/Library/Frameworks" install the templates that come with the SDL-devel-1.2.14-extras.dmg and now you can launch Xcode and chose a SDL template. Should compile and link successfully.

Why Windows OS annoys me...

2009-10-08T10:29:00.005+01:00

I was reading news were a windows system went down contaminated by a virus and was promptly replaced by a linux system. Thinking that someone has changed from windows to another operating system made me feel good.

But why did I feel good about it? Windows 3.1 gave GUI to the masses. Windows XP was a nice OS. Most computer games that I loved to play were running on windows. So where did this windows rejection come from?

I realize now that my repulsing instinct to windows OS is caused by my non-technical friends. As a computer guy all my friends tend to call me when their computer fail and they all use windows. The main cause for the windows miss behavior was usually a virus or other malware.
This leads me to the conclude that the main weak point of the Microsoft OS is it being the main target of malware industry and the non-tech users that tend to annoy their tech-friend.

How to hot-code-swap with erlang

2009-07-27T17:57:00.005+01:00

One of the most famous features of erlang is hot code swap.
What we'll do is open a shell into the running process and then load the new code.

The application must have been launched with -name app_name flag
Compile your code
Launch an erlang shell with:
> erl -name name_of_this_shell -remsh name_of_remote_process@remote_process_host
Load the new module with:
> l(module_name).

Simple!?

How I fell in love with computers and programming

2009-07-23T17:02:00.002+01:00

When I was a little boy I wanted to know how my toys worked, how can you make music from instruments or even how was it possible to animate drawings. And I spent long hours disassemble and trying to reassemble every thing that I could reach, drawing what I saw and making music with my toys.

One day I had a revelation - my uncle showed me his zx-spectrum. It was like a all-in-one thing. The possibilities were infinite. I thought that "It's amazing. I just have to tell it what to do and he'll do it for me!". Since then I've been happily making programs, music and graphics with computers.

Why Erlang, Axum, X10, Scala, Clojure...

2009-06-09T19:47:00.006+01:00

Lately I've been programing in Erlang and I really like it. But recently I became aware that big companies out there are making a huge effort in developing computer languages that try to simplify the complexity of concurrent programing. But this is what erlang is so good at.

The question that comes to my mind is "why not use Erlang?". The first thing I thought was that maybe there is something really broken in erlang that I'm not aware of. But if that was true, then big websites like FaceBook and LastFM wouldn't be adopting erlang with so good results.

Well what is it that Axum (Microsoft), X10 (IBM), Scala (EPFL), Clojure (Rich Hickey) try to give us that we don't already have with erlang. Some of them try to keep the OOP methodology and add some concurrent primitives. Others try to have a concurrency oriented language integrated with their favorite virtual machine or framework.

It's great to see so many people working in new languages. But will this quantity of new comers bring new and refreshing ideas or just scatter the community of developers.

Maybe Erlang developers just had the vision to the future more than 20 years ago (1986) when working for ericsson and now all the other kids of the neighborhood want to have the same toy.

Once again "time will tell".

jEdit syntax highlighting for erlang

2009-05-12T18:57:00.005+01:00

Just updated the jedit mode for erlang (just look for the file "modes/erlang.xml" under your jedit installation folder).

Added some keywords (is_float, is_atom, ...) and constant recognition (?DB_NAME).

Unfortunately blogger doesn't allow me to post the file, so I'll just publish the constant recognition code.


<SEQ_REGEXP HASH_CHAR="?"
   TYPE="LABEL"
   AT_WORD_START="TRUE"
  >\?.\w*</SEQ_REGEXP>

PS: Also there is no way to post code without having to use some "tricks". I'm annoyed.

Pylons more Alpha then Beta

2008-09-06T09:41:00.008+01:00

For the last couple of days I've been trying out pylons web framework (v0.97).

I decided to followed the official pylons book. At first I found some small glitches but I managed to work them around quite easily. This gave me more confidence that I was ready for pylons and pylons was ready for me. Since pylons and the book are still in Beta version I expected some small problems, but at after a wile the fixes were not so simple and I was wishing that something started to work without needing fixes.

I like the pylons concept of not reinventing the wheel, but after this experience I know that I can't use it to build a serious and complex web application. At least for now.

Next I'll be trying django.

It’s time to make time

2008-08-22T10:49:00.003+01:00

Some inspiring articles:

Make time

Achieve any Goal

Portuguese one

I made it, therefore I exist !

Death in the lunch break

2008-08-20T12:06:00.005+01:00

Yesterday lunch was quite an experience. Me and My colleges went to the mall were we could feed cheap and fast. Nothing special until we noticed that there were some fireman trying to reanimate a guy.
What choked me most, was the people eating while that guy was dying. I didn't know how to react. What could I do? Also the mall security was trying to hide the morbid scene piling up some tables and chairs around the fireman that were performing reanimation massage on the corps.
In the end the guy died just next to us and it was like nothing had append. No one knew him, no one cared.
What strange world we live in...

Brain Network

2008-06-01T20:29:00.004+01:00

Last week I attended to the BarCampFCT. It was very informal and as a result there was a more intimate atmosphere. It was quite different from the Takeoff2008.

It was very interactive and every one had to create a concept and make a presentation (Half Baked). Aldo no golden business opportunity came up, it reveal a great creative potential.

The usual suspects were all present.

I had to leave early and didn't assist to the ignite presentations. (shame on me)

In conclusion, these kind of events are a good brain stimulation that I don't want to miss.

I'm still alive !!

2008-05-02T09:07:00.004+01:00

Last Monday (28 of April) I was hit by a car wile driving my motorbike to work. I ended up on the hospital and my bike on the garage. Luckily I didn't brake any bone and besides the bruises I feel fine. A little depressed but fine.
Now I have to take care of a lot of bureaucracy and go everywhere by foot or public transports.
The good thing is "I'm still alive !!".

I'm alive

2008-04-20T15:32:00.000+01:00

Hi, this is my first post.
I decided to create this blog to share some ideas and some opinions.
This weekend I was in a conference Take Off 2008 at Coimbra University. There I realized that I need a blog to express myself on-line.
So this was the first step, now I need the ideas.

See you soon.