Skip to content

Category: english

OpenSolaris SVG Poster

Published by Silveira on 2008-03-28

Sometimes we just need an good template for organizing a OpenSolaris event, I didn’t found a good one in a reusable format so I did this empty OpenSolaris SVG Poster.

OpenSolaris SVG Poster
Download the svg file: opensolaris_poster.svg

But why an SVG poster? SVG means Scalable Vector Graphics, an XML specification and file format for describing two-dimensional vector graphics. If you use a typical bitmap format like png, gif or jpg and need to scale the image you will loss image quality.

Example of loss of image quality in a bitmap format

Using a vector graphics format you can scaled the image indefinitely without loss of image quality.

Example of loseless quality in svg image

Additionally is a free and open format and also very reusable. You can edit and use it in a broad set of tools, from a scalable image editor like Inkscape to, believe it or not, Netbeans!

OpenSolaris Vending Machine

Published by Silveira on 2008-03-27

Takadonobaba Vending Machines, Creative Commons Photo by Abuckingham, Flickr user
Vending Machines, Creative Commons photo by Abuckingham

Those days I was walking in a college to a tech demo and saw a lot of vending machines for soft drinks, coffees and snacks. So I thought “For a college student can be easier get a soda than a free software copy, like opensolaris”. Wouldn’t be nice if we have an OpenSolaris vending machine?

I sketched this idea:

OpenSolaris Vending Machine
OSVM, Open Solaris Vending MachineBut notice that is not just an CD/DVD vending machine. The OSVM could deliver the newest version of the OpenSolaris distributions to places where internet connections aren’t easy or cheap enough to download entire DVD images. A way to deliver open software to people who would have otherwise not been able to acquire it! Just choose, pay and get your free software.Press button, Receive bacon OpenSolaris.

Conceptual sketch of the opensolaris vending machine

Inside the machine:

  1. Switch
  2. External Internet connection
  3. Touch screen monitor
  4. Coolers
  5. Coolers
  6. Uninterruptible power supply
  7. External power source
  8. DVDs supply
  9. Money chest
  10. Paper money recognition device
  11. DVD Recorder
  12. OpenSolaris computer

Main challenges:

  • It’s necessary an broad internet connection (item 2) so the vending machine can have allways the last builds of each distribution (Indiana, Nevada, Nexenta, Solaris Express, etc). In places where this connection is not available someone should periodically supply the vending machine with more iso images.
  • The idea of using an touch screen monitor (item 3) is having a very usable and rich user interface.
  • The user should pay for using a paper money recognition device (item 10). I don’t know much about those devices but I guess you just buy an money recognition box that do this for you. After payed the money goes to some kind of chest (item 9).
  • The media should come from the supply (item 8 ) to the recorder (item 10) and so be delivered for the user. But how?
  • An technology such LightScribe would just fits perfectly in this machine.
  • The OpenSolaris computer (item 12) should be capable to store and manage all dvd iso images from each distributions. A reliable filesystem like ZFS would help.
  • A software to manage the downloading of each distribution periodically.
  • A software to provide a rich user interface, easy and nice to use. JavaFX should fits well.

Haven’t I see this before?

Someho, yes, some similar idea. IBM did a similar project some year ago and there’s too the cool Freedom Toaster that is similar in some points.

What is all about?

Is just a open idea. You can comment, suggest and I’d love to see that implemented.

Update 20.Out.2008: Thanks for those who are helping this idea and giving more ideas. Specially thanks for Everton Rodrigues. Maybe in some time we have an prototype.

Some useful links

Ruby: A Simple Example of Meta Programming

Published by Silveira on 2008-03-26

A really cool piece of code I read today in the book Ruby on Rails: Up and Running.

class Talker
  def method_missing(method)
     if method.to_s =~ /say_/
       puts $'
     end
  end
end

t = Talker.new

t.say_hello
t.say_something
t.say_goodbye

And running

$ ruby Talker.rb
hello
something
goodbye

But why do that when we have parameters? Because you can do some methods really dynamic with a clear semantic, just looking for them you know are they are doing.

Java assertion to prevent time travelers

Published by Silveira on 2008-03-23

cc broken pocket watches
Creative Commons photo by jekemp

public class PreventTimeTravelers {
    public static void main(String args[]){
        long startTime = System.currentTimeMillis();
        long endTime = System.currentTimeMillis();
        assert endTime >= startTime: "We came back in time!";
    }
}

Please do not execute this code in a time machine.

NumberFormatException Example

Published by Silveira on 2008-03-21

NumberFormatException: Thrown to indicate that the application has attempted to convert a string to one of the numeric types, but that the string does not have the appropriate format.

An simple example:

public class SummationExample {
    public static void main(String args[]){
        int sum = 0;
        for(String arg: args){
            System.out.println("+" + arg);
            sum += Integer.parseInt(arg);
        }
        System.out.println("= " + sum);
    }
}

$ javac SummationExample.java
$ java SummationExample 1 2 3 4 5
+1
+2
+3
+4
+5
= 15

but

$ java SummationExample 1 2 3 4 five
+1
+2
+3
+4
+five
Exception in thread “main” java.lang.NumberFormatException: For input string: “five”
at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:447)
at java.lang.Integer.parseInt(Integer.java:497)
at SummationExample.main(SummationExample.java:6)

So

public class SummationExample {
    public static void main(String args[]){
        int sum = 0;
        for(String arg: args){
            try {
                sum += Integer.parseInt(arg);
                System.out.println("+" + arg);
            } catch (NumberFormatException e) {
                // nothing
            }
        }
        System.out.println("= " + sum);
    }
}

now

$ javac BetterSummationExample.java
$ java BetterSummationExample 1 2 3 4 5
+1
+2
+3
+4
+5
= 15

and also

$ java BetterSummationExample 1 2 3 4 five
+1
+2
+3
+4
= 10

Java Duke animated gif waving

JRuby simple example

Published by Silveira on 2008-03-21

JRuby is a Java implementation of the Ruby interpreter, with an tightly integrated with Java. In this examples you will call swing components.

On Ubuntu you can get it installing the package jruby (a meta package for jruby1.0 or jruby0.9 packages).

To test it save this code as test.rb and invocate it with the jruby interpreter:

require 'java'

frame = javax.swing.JFrame.new()
frame.getContentPane().add(javax.swing.JLabel.new('Hello, JRuby World!'))
frame.setDefaultCloseOperation(javax.swing.JFrame::EXIT_ON_CLOSE)
frame.pack()
frame.set_visible(true)

$ jruby1.0 test.rb

Hello JRuby World

ps: We did not define a close method, so to close this windows you’ll need to kill its process or press Ctrl+C in your terminal.

List of popular programming book acronyms

Published by Silveira on 2008-03-20

I found cool this list on reddit.

  • AIMA Artificial Intelligence a Modern Approach by Stuart Russell and Peter Norvig
  • AMOP The Art of the Meta Object Protocol by Gregor Kiczales
  • ATTAPL Advanced Topics in Types and Programming Languages by Benjamin C. Pierce
  • AWDWR Agile Web Development with Rails by by Dave Thomas and David Heinemeier Hansson
  • EOPL Essentials of Programming Languages by Daniel P. Friedman, Mitchell Wand, and Christopher T. Haynes
  • CLR Introduction to Algorithms by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest
  • CLRS Introduction to Algorithms, 2nd Edition by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Cliff Stein
  • CLtL Common Lisp the Language by Guy L. Steele Jr.
  • CTM Concepts, Techniques, and Models of Computer Programming by Peter Van Roy and Seif Haridi
  • GOF Design Patterns by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides (the Gang of Four)
  • HOP Higher-Order Perl by Mark Jason Dominus
  • HTDP How To Design Programs by Matthias Felleisen, Robert Bruce Findler, Matthew Flatt and Shriram Krishnamurthi
  • K&R The C Programming Language by Brian Kernighan and Dennis Ritchie
  • LiSP Lisp In Small Pieces by Christian Queinnec
  • LL Lessons Learned in Software Testing by Cem Kaner, James Bach and Bret Pettichord
  • PAIP Paradigms of Artificial Intelligence Programming by Peter Norvig
  • PCL Practical Common Lisp by Peter Seibel
  • PLP Programming Language Pragmatics by Michael L. Scott
  • SICP Structure and Interpretation of Computer Programs by Hal Abelson and Gerald J. Sussman, with Julie Sussman
  • TAOCP The Art Of Computer Programming by Donald E. Knuth
  • TAPL Types And Programming Languages by Benjamin C. Pierce
  • TCPL The C++ Programming Language by Bjarne Stroustrup
  • TCS Testing Computer Software by Cem Kaner, Jack Falk, and Hung Quoc Nguyen
  • TLS The Little Schemer by Daniel P. Friedman and Matthias Felleisen
  • TSPL The Scheme Programming Language by R. Kent Dybvig
  • TSS The Seasoned Schemer by Daniel P. Friedman and Matthias Felleisen
  • TRS The Reasoned Schemer by Daniel P. Friedman, William E. Byrd and Oleg Kiselyov
  • WELC Working Effectively with Legacy Code by Michael Feathers

Graduation Party

Published by Silveira on 2008-03-20

Silveira Neto, Heraldo Carneiro and Cassiano Carvalho
Me, Heraldo Carneiro and Cassiano Fontenele.

Gorila (me) and Deborah
I’m the furry one with my girlfriend.

This year I’ll be graduated in Computer Science by UFC. We anticipate the party so we all can come. Was really a wonderful party. Thanks all made this celebration possible.

Below some photos from my graduation party.

You can see all photos on it’s album.

Pointers to functions in C++

Published by Silveira on 2008-03-16

I need to implements some codes in C++. Just remembering some concepts like pointers to functions.

A simple example:

#include <stdlib.h>
#include <iostream>

using namespace std;

double evalFunction(double (*f)(double), double param){
    return f(param);
}

double function(double x){
    return x/2;
}

int main(int argc, char** argv) {
    cout << function(5.0) << endl;
    cout << evalFunction(function, 5.0) << endl;
    return (EXIT_SUCCESS);
}