2. Function Overloading
C++ permits the use of two function with the same name.
However such functions essentially have different argument list.
The difference can be in terms of number or type of arguments or
both.
The biggest advantage of overloading is that it helps us to
perform same operations on different datatypes without having
the need to use separate names for each version.
This process of using two or more functions with the same name
but differing in the signature is called function overloading.
But overloading of functions with different return types are not
allowed.
In overloaded functions , the function call determines which
function definition will be executed.
3. Function Overloading
Example:
#include<iostream>
using namespace std;
int abslt(int );
long abslt(long );
float abslt(float );
double abslt(double );
int main()
{
int intgr=-5;
long lnt=34225;
float flt=-5.56;
double dbl=-45.6768;
cout<<" absoulte value of "<<intgr<<" = "<<abslt(intgr)<<endl;
cout<<" absoulte value of "<<lnt<<" = "<<abslt(lng)<<endl;
4. cout<<" absoulte value of "<<flt<<" = "<<abslt(flt)<<endl;
cout<<" absoulte value of "<<dbl<<" = "<<abslt(dbl)<<endl;
}
int abslt(int num)
{
if(num>=0)
return num;
else
return (-num);
}
long abslt(long num)
{
if(num>=0)
return num;
else return (-num);
}
float abslt(float num)
{
if(num>=0)
return num;
else return (-num);
}
double abslt(double num)
5. if(num>=0)
return num;
else return (-num);
}
OUTPUT
absoulte value of -5 = 5
absoulte value of 34225 = 34225
absoulte value of -5.56 = 5.56
absoulte value of -45.6768 = 45.6768
The above function finds the absolute value of any number int, long, float ,double.
The use of overloading may not have reduced the code complexity /size but has
definitely made it easier to understand and avoided the necessity of remembering
different names for each version function which perform identically the same task.
6. Call by Value & Call by Reference
In C ++ programming language, variables can be
referred differently depending on the context. For
example, if you are writing a program for a low
memory system, you may want to avoid copying
larger sized types such as structs and arrays when
passing them to functions. On the other hand,
with data types like integers, there is no point in
passing by reference when a pointer to an integer
is the same size in memory as an integer itself.
Now, let us learn how variables can be passed in
a C program.
7. Call By Value
When you use pass-by-value, the compiler copies the value of an
argument in a calling function to a corresponding non-pointer or non-
reference parameter in the called function definition. The parameter in the
called function is initialized with the value of the passed argument. As long
as the parameter has not been declared as constant, the value of the
parameter can be changed, but the changes are only performed within the
scope of the called function only; they have no effect on the value of the
argument in the calling function.
In the following example, main passes func two values: 5 and 7. The
function func receives copies of these values and accesses them by the
identifiers a and b. The function func changes the value of a. When control
passes back to main, the actual values of x and y are not changed.
8. Sample Program
#include <stdio.h>
void func (int a, int b)
{
a += b;
printf("In func, a = %d b = %dn", a, b);
}
int main(void)
{
int x = 5, y = 7;
func(x, y);
printf("In main, x = %d y = %dn", x, y);
return 0;
}
The output of the program is:
In func, a = 12 b = 7
In main, x = 5 y = 7
9. Call By Reference
There are two instances where a variable is passed by reference:
When you modify the value of the passed variable locally and also the
value of the variable in the calling function as well.
To avoid making a copy of the variable for efficiency reasons.
Passing by by reference refers to a method of passing the address of an
argument in the calling function to a corresponding parameter in the
called function.
In C, the corresponding parameter in the called function must be
declared as a pointer type.
In C++, the corresponding parameter can be declared as any reference
type, not just a pointer type.
In this way, the value of the argument in the calling function can be
modified by the called function.
10. Sample Program
The following example shows how arguments are passed by reference. In C++,
the reference parameters are initialized with the actual arguments when the
function is called. In C, the pointer parameters are initialized with pointer values
when the function is called.
#include <stdio.h>
void swapnum(int &i, int &j) {
int temp = i;
i = j;
j = temp;
}
int main(void) {
int a = 10;
int b = 20;
swapnum(a, b);
printf("A is %d and B is %dn", a, b);
return 0;
}
11. Call by Value vs Call by Reference
The process of calling The process of calling
function by actually sending function using pointers to
or passing the copies of pass the address of
data. variables .
At most one value at a time Multiple values can be
can be returned to the returned to calling function
calling function with an and explicit return
explicit return statement. statement is not required .
Here formal parameters are Here formal parameters are
normal variable names that pointer variables that can
can receive actual receive actual parameter or
parameters/argument arguments as address of
value’s copy. variables .
12. Calling a Function using a Pointer
In C++ you call a function using a function
pointer by explicitly dereferencing it using the *
operator. Alternatively you may also just use the
function pointer's instead of the funtion's
name. In C++ the two operators .* resp. ->* are
used together with an instance of a class in
order to call one of their (non-static) member
functions. If the call takes place within another
member function you may use the this-pointer.
13. Calling a function using a pointer
EXAMPLE:-
main()
{
TMyClass instance1;
int result3 = (instance1.*pt2Member)(12, 'a', 'b'); // C++
int result4 = (*this.*pt2Member)(12, 'a', 'b'); // C++ if this-pointer can
be used
TMyClass* instance2 = new TMyClass;
int result4 = (instance2->*pt2Member)(12, 'a', 'b'); // C++, instance2 is a
pointer
delete instance2;
return 0;
}
14. Pass Object As An Argument
Like any other data type,an object may be used as
a function argument.This can be done in two
ways:
-> A copy of the entire object is passed to the
function
-> Only address of the object is transferred to
the function
The pass by referrence method is more efficient
since it requires to pass only the address of the
object and not the entire object
15. Sample Program
/*C++ PROGRAM TO PASS OBJECT AS AN ARGUMEMT. The program Adds the
two heights given in feet and inches. */
#include< iostream.h>
#include< conio.h>
class height
{
int feet,inches;
public:
void getht(int f,int i)
{
feet=f;
inches=i;
}
void putheight()
{
cout< < "nHeight is:"< < feet< < "feett"< < inches< < "inches"< < endl;
}
