Interaction between Function
The main() function and other function are
interact with each other through parameter we pass the
parameter to the
function for the communication of calling function and call function .
the interaction
can take pace through :
1. Call by value.
2. Call by reference .
3. Return by reference .
4. Default argument .
5. Constant parameter.
6. Passing pointer.
Call By Value:-
Like c language C++ also
provides a call by value technique of parameter passing.
During the function call the values of actual parameter gets copied into
formal passing.
Any change made to formal parameter does not affect to actual parameter.
Swapping program done by call
by value.
#include
<cstdlib>
#include<iostream>
using
namespace std;
void
swap(int n1, int n2)
{
int temp;
temp=n1;
n1=n2;
n2=temp;
cout<<"\nAfter
swap : ";
cout<<"\t"<<n1<<"\t"<<n2;
}
int main(int
argc, char** argv) {
int
num1,num2;
void
swap(int,int);
cout<<"enter
two numbers ";
cin>>num1>>num2;
cout<<"before
swap : ";
cout<<"\t"<<num1<<"\t"<<num2;
swap(num1,num2);
cout<<"\n";
return 0;
}
****************************************
Output
enter two
numbers 5 4
before swap
: 5 4
After swap
: 4 5
Call By Reference:-
The disadvantage
of call by value technique of parameter passing is we can not return more than
1 value by called function.
With call by
reference technique of parameter passing we can not return more than one value but we can directly change the
respective value.
In this
method of passing parameter if any change made in formal parameter that affects
the actual parameter.
Program for
swapping two variable using call by reference.
* Author:
ROHAN
*
* Created on July 11, 2018, 12:14 PM
*/
#include
<cstdlib>
#include<iostream>
using
namespace std;
void
swap(int &n1, int &n2)
{
int temp;
temp=n1;
n1=n2;
n2=temp;
cout<<"\nAfter
swap : ";
cout<<"\t"<<n1<<"\t"<<n2;
}
int main(int
argc, char** argv) {
int
num1,num2;
void
swap(int&,int&);
cout<<"enter
two numbers ";
cin>>num1>>num2;
cout<<"before
swap : ";
cout<<"\t"<<num1<<"\t"<<num2;
swap(num1,num2);
cout<<"\n";
return 0;
}
***********************************************
Output/
enter two
numbers 4 5
before swap
: 4 5
After swap
: 5 4
Constant Argument:-
The constant
value as a function argument is passing using ‘const ‘ qualifier.
This tell to
compiler that function should not modified the argument .
If the value
change compiler gives an error .
Program to
find area of circle without const
/* Author:
ROHAN
*
* Created on July 11, 2018, 1:12 PM
*/
#include
<cstdlib>
#include<iostream>
using
namespace std;
float area
(int r, float p)
{
p=0;
return(p*r*r);
}
int main(int
argc, char** argv) {
int rad;
float pi=3.24;
float a;
float
area(int ,const float);
cout<<"Enter the radius :
";
cin>>rad;
a=area(rad,pi);
cout<<"the areaof circle :
"<<a;
return 0;
}
**********************************************
output
Enter the
radius : 5
the areaof
circle : 0
Program
with constant
/*
* File:
main.cpp
* Author: ROHAN
*
* Created on July 11, 2018, 1:12 PM
*/
#include
<cstdlib>
#include<iostream>
using
namespace std;
float area
(int r,const float p)
{
return(p*r*r);
}
int main(int
argc, char** argv) {
int rad;
const float pi=3.24;
float a;
float area(int ,const float);
cout<<"Enter the radius :
";
cin>>rad;
a=area(rad,pi);
cout<<"the areaof circle :
"<<a;
return 0;
}
****************************************************
Output
Enter the
radius : 5
the areaof
circle : 81
Default argument:
C++ allow to pass default argument to function ,so lets
see the syntax and program.
Syntax:
Datatype function
name(datatype=value);
float amount(float
a=30,int p);
program addition
using default argument
/* Author:
ROHAN
*
* Created on July 11, 2018, 1:33 PM
*/
#include
<cstdlib>
using
namespace std;
#include<iostream>
using
namespace std;
int main()
{
int add (int
a,int b=20,int c=30,int d=40);
cout<<add(10)<<endl;
cout<<add(10,5)<<endl;
cout<<add(1,2,3)<<endl;
return 0;
}
int add (int
p, int q, int r, int s)
{
return (p+q+r+s);
}
********************************************************
Output
100
85
46
Passing pointer to function:-
C++ allows
to pass pointer to function, so lets see directly by doing program. How to pass
pointer to the function.
#include<iostream>
#include<ctime>
using
namespace std;
void get(int
*p);
int main()
{
int s=10;
get(&s);
cout<<"Number
of second : "<<s<<endl;
return 0;
}
void
get(int *p){
*p=time(NULL);
return;
}
*********************************************
Output:
Number of
second : 1531331852
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