Functional Programming-Call by Value

After defining the function, there is a need to pass the arguments into the function to get the desired output. All the programming language supports the call by value and call by reference methods after arguments passed into the functions.

"Call by value" works only on the object-oriented programming language like C++. Functional programming language like Python also supports "call by value".

The original value of the call by value method will not change when we pass the arguments to the function. The function will store the value locally through the function parameter in stack's memory. The changed value in the function will not affect functions from the outside.

Call by Value in C++

Here is the program which shows the call by value in the C++.

#include<iostream.h>
#include<conio.h>

void swap(int x, int y)
{
 int temp;
 temp=x;
 x=y;
 y=temp;
}

void main() 
{  
 int x=400, y=600;  
 clrscr();  
 swap(x, y);  // arguments passed to the function
 cout<<"Value of x"<<x;
 cout<<"Value of y"<<y;
 getch();  
}  

This will show the following output:

Value of x is: 200
Value of y is: 100

Call by Value in Python

Below program shows the working of Call by Value in Python:

def swap (x, y):
t = x;
x = y;
y = t;
print " the value of x argument inside the function: ", x
print " the value of y argument inside the function: ", y
# Now we will call swap function
x = 70
y = 75
print " the value of x argument before assigning into function: ", x
print " the value of y argument before assigning into function: ", y
swap (x, y)
print " the value of x argument after assigning into function: ", y
print " the value of y argument after assigning into function: ", x

The output of the above program will look like as shown below: