A one line Python Quine

OK, Here's a one line Python program that prints its own source code:

s='s=%r;print s%%s';print s%s

This wikipedia article on Quines is a very good place to learn how these things work

One line quicksort in Python

Here's a one line quicksort in python. I came up with this idea after looking at a 2 lines implementation in Haskel

qsort = lambda seq: [] if not seq else qsort(filter(lambda n: n<=seq[0], seq[1:]))+[seq[0]]+qsort(filter(lambda n: n>seq[0], seq[1:]))

What goes around comes around

 

Image source: http://www.facebook.com/group.php?gid=202376966626&ref=mf

5 Handy python functions (lambdas)

Here's a list of 5 handy python lambda's you may need when solving a quick maths problem

1) The sum of all integers from 1 to n

triangle = lambda n: n*(n+1)/2

2) Factorial

factorial = lambda n: 1 if n<2 else n*factorial(n-1)

3) Get odd numbers

odds = lambda n: [k for k in range(1,n,2)]

4) Test whether a number is prime

is_prime = lambda n: False if n<2 else (0 not in [n%k for k in range(2,int(n**.5)+1)])

A number is prime when it has no factor other than 1 and itself. To determine whether the number is a prime, we need to check that it doesn't leave a reminder of 0 when divided by each number in the range of [2..square root of the number].

5) Primes sieve
This function returns the list of primes in the range [2..N]. It's the most cryptic of all but it makes use of the previous function to add a number to the generated list.

sieve = lambda n: [k for k in range(2,n+1) if (0 not in [k%i for i in range(2,int(k**.5)+1)])]

It could also be written as:

is_prime = lambda n: False if n<2 else (0 not in [n%k for k in range(2,int(n**.5)+1)])

sieve = lambda n: [k for k in range(2,n+1) if is_prime(k)]

Let’s cook a simple yet powerful HTML Editor with Delphi

N.B. You might need to read Using Scintilla in Delphi 7 before reading this tutorial.

I'm cooking a simple WYSIWYG HTML Editor which allows editing a webpage from design mode and source mode just like FrontPage and DreamWeaver do. Things like auto-completion, Style editor and flash are beyond the scope of this tutorial.

When cooking a simple IDE, syntax highlighting is the ingredient that makes it different from a text editor like notepad. If syntax highlighting never existed and all we had was notepad, I don't think I would have learnt HTML.

Step 1: Warm the interface
Drop a TScintilla (from the Scintilla tab), a TWebBrowser (from the Internet tab) , 3 buttons and a TOpenDialog on the form.
Set the language of the Scintilla control to HTML. So you should have something like this:

The first button will be for loading the file you want to edit, the second for refreshing the Preview and the third for switching to design mode.

Step 2 (Add some code)
In order to get juice out of the TWebBrowser component, you must add the mshtml unit to the code. This unit is interesting because it exposes some of the stuff that make up the engine used by Internet Explorer and other Microsoft programs. An expert HTML user will be very familiar with some of the methods and properties in this module. Here’s the code:

implementation
{$R *.dfm}
uses
  mshtml;

Step 2 (Loading the HTML file)
the first button will simply load an html file onto the webbrowser. Add this code for the Click Event on button1:

procedure TForm1.Button1Click(Sender: TObject);
var
  doc: IHTMLDocument2;
begin
  if not OpenDialog1.Execute then
     Exit;

  WebBrowser1.Navigate(OpenDialog1.FileName);
  doc:= WebBrowser1.Document as IHTMLDocument2;

  while doc.readyState <> 'complete' do Application.ProcessMessages;

  Scintilla1.Lines.Text:= doc.body.innerHTML;
end;

To load the file I used WebBrowser1.Navigate(OpenDialog1.FileName);
Because I’ll need to retrieve the text from the WebBrowser at some stage, I used a IHTMLDocument2 interface to allow me to read the innerHTML of the document’s body. The head isn’t much needed here. Unfortunately the outerHTML property of the body is read-only. This pauses a problem because I can’t edit attributes set in the tag. You can use file handling routines or another method to be able to access the full source code but we'll stick to this simple method from its simplicity.

The line while doc.readyState <> 'complete' do Application.ProcessMessages; is useful because we’ll get an exception if we try to use the body element because it becomes ready.

Running the program should give you something like this:

Step 3 (I can smell it)
Now I can edit the html but nothing will happen if I try to preview.
So to connect the two controls, I’ll write the code for button2. It copies the text  from the scintilla control into the innerHTML of the document’s body.

procedure TForm1.Button2Click(Sender: TObject);
var
  doc: IHTMLDocument2;
begin
  doc:= WebBrowser1.Document as IHTMLDocument2;
  doc.body.innerHTML:= Scintilla1.Lines.Text;
end;

Now you can test the source code editor. But get the WYSISWYG part we got to the Next step…

Step 4 (The food is ready)

The last button will switch the designMode ‘on’ for the WebBrowser:

procedure TForm1.Button3Click(Sender: TObject);
var
  doc: IHTMLDocument2;
begin
  doc:= WebBrowser1.Document as IHTMLDocument2;
  doc.designMode:= 'on';
end;

 OK, That's it! We get this:

Using Scintilla in Delphi 7

Scintilla is a cool open source text editing control which supports syntax highlighting, code folding, auto-indentation, line numbers and many more features.

A list of projects using scintilla can be found on their website (http://www.scintilla.org/ScintillaRelated.html).
To use Scintilla in Delphi you must install Delphi Scintilla Interface Components
 a.k.a delphisci which is no longer under development but since Delphi 7 itself is older, this shouldn’t be a problem.

Step 0
I’ll use the following names in this tutorial:
 - DELPHI_INSTALLATION_FOLDER: The folder where your Delphi is installed
 - SYSTEM32: C:\Windows\System32
 - DELPHI_SCI_FOLDER: The folder where you unzip delphisci

Step 1 (Getting ready)

Get a copy of delphisci from sourceforge, unzip it and inside the unzipped folder, there should be a zip file called scilexer_precompiled_171CVS which contains scilexer.dll (the only external dependency) and put this scilexer.dll in SYSTEM32 if there isn’t one yet.

Step 2 (Installation)

In DELPHI_SCI_FOLDER, there's file names INSTALL which has the instructions for installing delphisci. Follow those instructions. If you struggle with that make sure you:

1. Compiled the right project group for the version of Delphi you are using.
   
2. Installed the package into Delphi (Components->Install Package-> [choose scitD7.bpk from DELPHI_INSTALLATION_FOLDER\Projects\Bpl or go to Tools->Environment Options->Library and ckeck where your Bpl Output Directory is])

Step 3 (Successfully running it)
If you successfully followed those instructions you should have a Scintilla tab on the components pallette but if you try to run any project using these Scintilla components you get a “[Fatal Error] … File not found: SciLexer.dcu”. That happens because you haven’t added the DELPHI_SCI_FOLDER \d7dcu folder to the Environment yet so Delphi is unable to locate these.

Step 3.14

To add the DELPHI_SCI_FOLDER \d7dcu folder to the Environment I’d normally create a folder in DELPHI_INSTALLATION_FOLDER\Scintilla and copy all the files from DELPHI_SCI_FOLDER \d7dcu into this new folder.

Step 3.5
Now on Delphi, go to Tools->Environment Options->Library and add DELPHI_INSTALLATION_FOLDER\Scintilla to the Library Path

Step 4 (Testing)
Now to test the installation, create a new application, drop some Scintilla controls to the form and Run it.

Step 5 (Using syntax highlighting)

When you first drop a TScintilla components on a form, it has no language set and getting the syntax highlighting to work took some working until I realised that you have to Right click on the control -> Select Prefered Languages -> Choose a language and press OK. Then on the property editor, expand the LanguageManager and on the SelectedLanguage drop-down pick the language you chose earlier.

And that's it!

Proceed to Let’s cook a simple yet powerful HTML Editor with Delphi for some action.

FIN

How to get a 3G modem working on Ubuntu 8.04 and other ubuntu's

In a blog post at tectonic that shows how to access to the internet with a 3G card through vodafone-mobile-connect-card-driver, I left a comment for those people struggling to get a permanent connection...

The instructions are found here

Here's my addition:

1. Plug in the card and restart the computer
2. On a terminal type: dir /dev/ttyUSB* and make sure you get something like this:
/dev/ttyUSB0
/dev/ttyUSB1
I found that the software seems to work perfectly only when /dev/ttyUSB0 and /dev/ttyUSB1 both refer to your 3G card. Other ttyUSB's don't seem to work for me
3. type sudo poff to make sure that all previous connections are closed. I used sudo because the vodafone-mobile-connect-card-driver-for-linux violates many permission rules when run as a normal user (the documentation told me that). Therefore sudo will grant him all the rights he needs.
4. type sudo vodafone-mobile-connect-card-driver-for-linux-debug so that you can see what’s going on. If the program seems to stop printing stuff on the terminal without having printed your contacts list yet, Try closing it and repeat steps 3 and 4.

Enjoy the web!