Variable Arguments

Plz help to Solve the following Questions

Is it possible variable arguments in C++ functions ,

What is the syntax and prerequired functions for this if yes....

Thanks!

There is support for variable argument lists inherited from C, except that the relevant standard header is <cstdarg> instead of <stdarg.h>. However, an idiom more common in C++ is to use function chaining instead. If you tell us why you are trying to use a variable argument list, perhaps we can tell you how to use function chaining instead.

int f(int, ... );

int f(int, ... ) {
.
.
.
}

int g() {
f(1,2,3);
}

Note that where it says '...' that's literally the symbol you use

I am thinking about the var:: arg function when i create a draw()...Different arg list for different shapes.so different fn() for different shapes....How to use fn chaining here ?

Quote:

---

Originally Posted by Dave1024

I am thinking about the var:: arg function when i create a draw()...Different arg list for different shapes.so different fn() for different shapes.

---

Why exactly would there be a different parameter list for each different shape? It sounds like an appropriate solution is to create an abstract base class with a pure virtual draw() member function, and then override it appropriately for each shape.

Ok Might be possible. But i have this situation

int Shape(int,int,int); Arguments For a Triangle

int Shape(int,int,int,int,int); Arguments For a Pentagon

int Shape(int,int,int,int,int,int) ;Arguments for a hexagon

this is ok with function overloading in C++;

Here var:: arg will avoid the overhead of overloading fns declaration and there is

one and only one fn Shape(int,...);

Is this an Advantage....?

Quote:

---

Originally Posted by Dave1024

But i have this situation

int Shape(int,int,int); Arguments For a Triangle

int Shape(int,int,int,int,int); Arguments For a Pentagon

int Shape(int,int,int,int,int,int) ;Arguments for a hexagon

this is ok with function overloading in C++;

---

I am not talking about function overloading. I am talking about virtual function overriding, e.g.,

Code:

---

class Shape
{
public:
    virtual ~Shape() {}
    virtual void draw(std::ostream& out) const = 0;
};

class Triangle : public Shape
{
public:
    Triangle(int x, int y, int z) : x(x), y(y), z(z) {}

    virtual void draw(std::ostream& out) const
    {
        out << "Triangle: " << x << ", " << y << ", " << z << '\n';
    }
private:
    int x, y, z;
};

class Pentagon : public Shape
{
public:
    Pentagon(int v, int w, int x, int y, int z) : v(v), w(w), x(x), y(y), z(z) {}

    virtual void draw(std::ostream& out) const
    {
        out << "Pentagon: " << v << ", " << w << ", " << x << ", " << y << ", "
            << z << '\n';
    }
private:
    int v, w, x, y, z;
};

---

Quote:

---

Originally Posted by Dave1024

Here var:: arg will avoid the overhead of overloading fns declaration and there is

one and only one fn Shape(int,...);

Is this an Advantage....?

---

What overhead are you talking about? Virtual functions do come with some overhead, but that does not apply to function overloading, other than more code. Besides, you cannot just provide 3 arguments for a triangle with a variable argument list. You need another argument to tell the function how many arguments there are.

Quote:

---

Originally Posted by Dave1024

Ok Might be possible. But i have this situation

int Shape(int,int,int); Arguments For a Triangle

int Shape(int,int,int,int,int); Arguments For a Pentagon

int Shape(int,int,int,int,int,int) ;Arguments for a hexagon

this is ok with function overloading in C++;

Here var:: arg will avoid the overhead of overloading fns declaration and there is

one and only one fn Shape(int,...);

Is this an Advantage....?

---

That looks like a broken design. If you have got only one shape class that can represent a triangle, a square and maybe some other shapes you better create one abstract shape base class and introduce a derived class for every concrete shape type. This is the example used by almost every C++ book I read to introduce polymorphism ;)