How to check the directory exists or not from Makefile??

If the directory exists means, no need to untar the file.

setup:

if test -d DIR_NAME ; then echo NO NEED TO UNTAR ; else tar -xvf FILE.tar ; fi

Singleton Design Pattern with example C++ code

The Singleton design pattern ensures only one instance of a class in an application. For example, Interfaces object need by both GUI and Back-end class. But only one interface object enough for the whole application (GUI + interface + Back-end)

Here need to develop the interface class as a Singleton class.

static CInterface *s_ptrInterface = 0;

class CInterface

{

private:

CInterface();

~ CInterface();

public:

static CInterface* getInterface()

{

 lock(); // for thread safe.

if( 0 != s_ptrInterface )

s_ptrInterface = new CInterface();

unlock();

return s_ptrInterface ;

}

}

Need to create the object for CInterface like below,

CInterface:: getInterface() // it’s always return the same object

Photograph Puzzle Maker

try this site,

http://www.flash-gear.com/npuz/

Object slicing example in C++

class Pet

{

string pname;

public:

Pet(const string& name) : pname(name) {}

virtual string name() const { return pname; }

virtual string description() const { return "This is " + pname; }

};

class Dog : public Pet

{

string favoriteActivity;

public:

Dog( const string& name, const string& activity): Pet(name), favoriteActivity(activity) {}

string description() const { return Pet::name() + " likes to " + favoriteActivity; }

};

void describe(Pet p)

{ // Slices the object

cout << p.description() << endl;

}

int main()

{

Pet p("Alfred");

Dog d("Fluffy", "sleep");

describe(p);

describe(d);

}