Compiling cpp with gcc

Hi,

I know the title is a bit confusing. But believe me, i am not trying to confuse :).

In very layman terms , g++ is nothing but a special version of gcc.

Ignoring all the complexities, the most trivial work it does is making cpp the default

language, which results in stdcpp library to get linked by default.

So, if you want to play a trick and compile your cpp code with gcc, just link the stdc++ lib by yourself.

$ gcc file1.cpp -lstdc++ -o output

This will do the trick.

Have tested it with basic helloworld, so if your complex template containing code doesn't compile with this, don't complain, more over you should give a thought about what template is actually doing to your code :).

The Old "new"

Remember the good old C days,

When after memory allocating code,

We had to check the pointer against NULL, just to make sure that the memory has actually been allocated.

int * arr = (int*)malloc(sizeof(int)*10);

if(arr==NULL)

{

// No memory allocated

}

Many people carry this habit from C to C++, which is not all together right.

As in CPP new operator throws an error, "bad_alloc" to be precise , in the case where memory was not allocated.

But if u like living in old days, and insist on comparing the pointer to NULL to check whether memory has been allocated or not. You can use

A * a = new(nothrow) A();

Now you can keep on reliving those times.

On a more serious note, this practise is not recommended in C++, but in some projects developed before C++ introduced "exception handling", this practise has to be continued.

Dual booting on my phone

Hi Guys,

Finally i was able to install NITDroid android port to N900.

Been trying for over 2 months now, the problem was with my SD card.

Anybody wanting to try it out ( and having a N900 is a must :) ), can go to the link given below.

http://wiki.nitdroid.com/index.php?title=N900-Autoinstaller

But having a wifi connection is a must, Data downloaded is over 100 MB.

Or there is another way.

Can download the required files on your PC.

Then on your "N900" open the terminal. Goto /home/user/MyDocs

Make folder named .nitdroid

paste all the files downloaded on the pc to this folder.

Then start the nitdroid installer, it will just pick up the files from the newly created folder.

Neat isn't it :)

Having a phone which dual boots is a dream come true, one of my ultimate tech fantasies.

Currently i have both Maemo 5 and NITDroid on my phone, and am waiting for meego community build for N900 to comes out sometime in october, so that i can triple boot and attain Moksha :)

NOTE: If anybody is facing problem post install in getting the NITDroid to work, try using some other SD Card, it might just work for you.

awk------ a jewel...

Hi,
Its been a long time friends, since i last posted.
So what's better to reboot the posting spree than Linux.

awk is the focus today.
This post is not supposed to be an extended tutorial, but just a reference for novices and first timers.

awk is not just a simple command, its an interpreter, well atleast sort of.
you can write awk scripts, and rule the world :)

consider a condition in which you want to print the second column of every line of the input, which can be a file or even the output of some command piped through.

ls -l | awk '{print $2}'

this command does it all, takes the input from ls command and prints the 2nd column.

and its just not that you can even use if/for/while etc.

So, jump into the depths of awk.
More is coming.

N900:- absolute beauty

Just got my brand new N900, and belive me friends when i say, AM LOVING IT.
Am writing this post from my N900 itself. This phone has got a variant of debian on it. And with intel and nokia's Meego OS coming soon, this phone will have a multiboot options in Maemo and Meego.

Will post more about my adventures with this wonderful device incourse.

Searching 2.0 ---- new frontiers

Searching has entered a new domain with introduction of Google's "Goggles" service, Although goggles is a comprehensive service using which we can make searches based on images, landmarks, books, logos etc... but we will be concentrating on the book title searching ( or any other search which concentrates on extracting text from images and then searching for it).

As far as searching for a book or textual logo goes it can be easily implemented using OCR to extract the text from the image and then searching the text which was earlier extracted from the image.

OCR stands for "Optical character recognition". It is widely used to convert books and documents into electronic files, to computerize a record-keeping system in an office, or to publish the text on a website. OCR makes it possible to edit the text, search for a word or phrase, store it more compactly, display or print a copy free of scanning artifacts, and apply techniques such as machine translation, text-to-speech and text mining to it. OCR is a field of research in pattern recognition, artificial intelligence and computer vision.

In this blog post, We will be discussing how to easily extract text from images ourselves and then implement out own visual searching service.

For the purpose of extracting text from the image we will be using The "Tesseract OCR engine". The Tesseract OCR engine was one of the top 3 engines in the 1995 UNLV Accuracy test. Between 1995 and 2006 it had little work done on it, but it is probably one of the most accurate open source OCR engines available. The source code will read a binary, grey or color image and output text. A tiff reader is built in that will read uncompressed TIFF images, or libtiff can be added to read compressed images.

As a wrapper for this engine we will be writing a script in python using an opensource python project called "PyTesser".

PyTesser is an Optical Character Recognition module for Python. It takes as input an image or image file and outputs a string.

PyTesser uses the Tesseract OCR engine (an Open Source project at Google), converting images to an accepted format and calling the Tesseract executable as an external script. A Windows executable is provided along with the Python scripts. The scripts should work in Linux as well.

The example we are going to discuss here is tested on python 2.5, but it should work with newer versions barring version 3.0.

Another component which needs to be added to the python2.5 is PIL. It is required to work with images in memory. PyTesser has been tested with Python 2.5 in Windows XP.

So, now moving on to more exciting part, i.e actually getting something done. Download and extract the PyTesser into the scripts folder of python25 dir. Tesseract OCR engine's binary is included with the PyTesser archive.

We have used IDLE editor for python coding, any other can be used. Eclipse too can be used for python development with "pydev" plugin installed.

After setting up the environment paste this code in the newly initiated project/file.

from pytesser import * # import all packages from pytesser script
image = Image.open('fnord.tif') # Open image object using PIL
print image_to_string(image) # Run tesseract.exe on image
print image_file_to_string('fnord.tif')


We have used the example image provided with the PyTesser package here. Running this code will analyze the image and after extracting the text embedded in the image will print it on the console.

So, now we have to use the extracted text for searching.

This relatively simple thing can be used for multiple scenarios, one can be getting info about the latest offer for a product, or searching for different branches of a chain of stores. Lets discuss the endless possibilities and unleash our creativity here.


Download Links:

python imaging library ( PIL ) : http://www.pythonware.com/products/pil/
PyTesser : http://code.google.com/p/pytesser/
Tesseract OCR engine : http://code.google.com/p/tesseract-ocr/

Structures and Classes in c++

struct keyword is facing the downside in comparison of class because of its strong attachment to the legacy C code.
But most people ignore the fact that structs have been totally reinvented in c++.

The only difference between struct and class in c++ is that by default everything is public in structs and private in classes, even the default inheritance in struct is public.

thats all the difference between structs and classes, then why in recent programming practices structs have been totally ignored.

structs can be safely initialized using constructors, they can have polymorphic nature, support late binding, in short everything you need to write good OO code.


check out the code given below.

#include
using namespace std;

struct Whatever
{
virtual void foo() { }
virtual ~Whatever() { }
};

struct Derived : Whatever
{
void foo() { cout << "value=" << value; }
Derived(int n) : Whatever(), value(n) { }

private:
int value; // private data member
};

int main()
{
Whatever *pW = new Derived(10);
pW->foo(); // virtual call
delete pW;
return 0;
}


IMHO struct are fighting a loosing battle because of the mindset of the developers, We have been taught C++ means classes, C++ even started out as "C with classes".
anything which needs an aggregate data type can be implemented using structs and anything needed as a complex data type adhering to OOPS principles, representing some real world object needs to be implemented in terms of classes.

There is no problem in using classes or structs for that matter, just need to open our minds to the realities of C++ , rather than following and believing in myths.