Difference between function overloading and default arguments?

Answer 1

A default constructor is one where no arguments are declared or required. Thus if all arguments have defaults then it is still a default constructor, but one that can also serve as an overloaded constructor.

Consider the following which has two constructors, one with no arguments (the default) and one with two arguments (an overloaded constructor):

struct A

{

A () : x (42), y (3.14) {}

A (const int a, const double b) : x (a), y (b) {} int x;

double y;

// ...

};

We can invoke these two constructors as follows:

A a; // invokes default constructor (a.x is 42, a.y is 3.14).

A b (0, 1.0); // invokes overloaded constructor (b.x is 0, b.y is 1.0).

Since both constructors are essentially doing the same thing, they can be combined into a single constructor -- we simply make the 'magic numbers' the default values of the overloaded constructor:

struct A

{

A (const int a=42, const double b=3.14): x (a), y (b) {}

int x;

double y;

// ...

};

A a; // a.x is 42, a.y is 3.14.

A b (0, 1.0); // b.x is 0, b.y is 1.0.

As far as the calling code is concerned, nothing has changed, but the class declaration is simplified by removing a redundant constructor.

Answer 2

In function overloading, for different tasks there should be different blocks of codes with the same name to perform different tasks, while default arguments has only one block of code and perform only one task.

Function overloading take different types & numbers of argument to perform different tasks, But default arguments perform only one task which has been declared or written for it without weather its called with exact number of parameters called with less number of parameters. but it will perform the same task.

Function overloading take the exact number of parameters to work, But default arguments can take exact number of parameter or less number of parameters or even no parameters. it will assign the default values to the parameters and perform the task.

Hope it will help you,

Please correct if there was mistake.

RAMIN SADAT, South Asian University (MSC)