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Type Casting in C++

The type casting of variables in the C++ programming language will be covered in this section. The term "type casting" describes how software converts one data type to another. There are two ways to typecast code: automatically by the compiler, and manually by the user or programmer. Type Conversion is another name for type casting.

Consider the situation when we wish to change the data from an integer type to a float type. Therefore, we must manually cast int data to the float type; in C++, this process is known as type casting.

int num = 5 ;  
float x ;  
x = float ( num ) ;  
x = 5 . 0  

Another example:

float num = 5 . 25 ;  
int x ;  
x = int ( num ) ;  

Implicit conversion, also known as Implicit Type Casting, and explicit type conversion, also known as Explicit Type Casting, are the two main forms of type casting.

Implicit Type Conversion vs. Implicit Type Casting

  • The automated type casting is what it is called.
  • Without any assistance from a user or programmer, it automatically converted between different data types.
  • It implies that a data type is automatically converted to another by the compiler.
  • Without sacrificing any information, every data type is immediately updated to the biggest kind.
  • It can only be used in a program if the two variables work well together.
char - sort int - > int - > unsigned int - > long int - > float - > double - > long double , etc. 

NOTE: Remember to do implicit type casting from lower to higher data types. Otherwise, it has an impact on the basic data type and may cause it to lose accuracy or data, in which case the compiler may flash a warning.

Example1: A program that makes advantage of C++'s implicit type casting

Let's construct an example to show how to cast one variable to another in C++ using implicit type casting.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;  
int main ( )  
{  
    short x = 200 ;  
    int y ;  
    y = x ;  
    cout << " Implicit Type Casting " << endl ;  
    cout << " The value of x : " << x << endl ;  
    cout << " The value of y : " << y << endl ;  
      
    int num = 20 ;  
    char ch = ' a ' ;  
    int res = 20 + ' a ' ;  
    cout << " Type casting char to int data type ( ' a ' to 20 ) : " << res << endl ;  
      
    float val = num + ' A ' ;  
    cout << " Type casting from int data to float type : " << val << endl ;   
    return 0 ;                                                                                     
}  

OUTPUT:

Implicit Type Casting
The value of x : 200
The value of y : 200
Type casting char to int data type ( ' a ' to 20 ) : 117
Type casting from int data to float type : 85
........................................................
Process executed in 2.11 seconds
Press any key to continue

Explanation

The short data type variable x is 200 and the integer variable y were both defined in the aforementioned application. After that, we assign the value of x to the value of y, at which point the compiler instantly translates x's short data value to y, returning y to be 200.

The character type variable ch is set to "a," which is equal to an integer value of 97, and the int type variable num is set to 20 in the following statements. The implicit conversion is then completed by adding these two variables, returning the expression's result of 117.

In the third statement, we do the same thing by adding the character variable ch to the integer variable num, which is 20, and assigning the result to the float variable val. As a consequence, the compiler automatically converts the expression's result to the float type.

Explicit Type Conversion vs. Explicit Type Casting

  • It is often referred to as a program's manual type casting.
  • Programmers or users must manually cast data to switch from one data type to another in a program.
  • It implies that a user may simply cast one data to another in accordance with a program's demand.
  • The compatibility of the variables need not be verified.
 (type) expression; //syntax of explicit casting
  • type: It symbolizes the user-defined information that transforms the supplied phrase.
  • expression: It symbolizes a constant value, variable, or expression whose data type has been changed.
int num ;      
num = ( int ) 4 . 534 ; // cast into int data type  
cout << num ;  

When the aforementioned commands are run, the cast () operator will convert the floating-point value into an integer data type. Additionally, the integer num that receives the float value is given a decimal truncation, showing just 4 as the integer value.

Example2: A program to show how to utilize C++'s explicit type casting

Let's make a straightforward program that uses the explicit type casting feature of the C++ programming language to convert a variable of one type into a different type.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;  
int main ( )  
{  
    // declaration of the variables  
    int a , b ;  
    float res ;  
    a = 21 ;  
    b = 5 ;  
    cout << " Implicit Type Casting : " << endl ;  
    cout << " Result : " << a / b << endl ; // it loses some information  
      
    cout << " \n Explicit Type Casting : " << endl ;  
    // use cast ( ) operator to convert int data to float  
    res = ( float ) 21 / 5 ;  
    cout << " The value of float variable ( res ) : " << res << endl ;  
      
    return 0 ;                             
}  

OUTPUT:

Implicit Type Casting :
Result : 4
Explicit Type Casting :
The value of float variable ( res ) : 4 . 2
........................................................
Process executed in 2 . 11 seconds
Press any key to continue

Explanation

Two integer variables, a and b, with the values 21 and 2, are used in the aforementioned program. Next, divide a by b (21/2), which yields a value of type 4 int.

Using the cast operator in the explicit type cast method, we define a float type variable res in the second expression that saves the outcomes of a and b without erasing any data.

Example3: Use the cast operator in a program to convert double data to int and float types.

Let's look at an example where double data is converted into float and int types in C++ programming to determine the area of a rectangle.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;  
int main ( )  
{  
    // declaration of the variables  
    double l , b ;  
    int area ;  
      
    / / convert double data type to int type  
    cout << " The length of the rectangle is : " << endl ;  
    cin >> l ;  
    cout << " The breadth of the rectangle is : " << endl ;  
    cin >> b ;  
    area = ( int ) l * b ; / / cast into int type  
    cout << " The area of the rectangle is : " << area << endl ;  
      
    float res ;  
    // convert double data type to float type  
    cout << " \n \n The length of the rectangle is : " << l << endl ;  
    cout << " The breadth of the rectangle is : " << b << endl ;  
    res = ( float ) l * b ; // cast into float type  
    cout << " The area of the rectangle is : " << res ;  
    return 0 ;                                                                                     
}  

OUTPUT :

The length of the rectangle is : 
57 . 3456
The breadth of the rectangle is :
12 . 9874
The area of the rectangle is : 740
The length of the rectangle is : 57 . 3456
The breadth of the rectangle is : 12 . 9874
The area of the rectangle is : 744 . 77
........................................................
Process executed in 2 . 31 seconds
Press any key to continue

Explanation

In the above example of a program in C++, we have demonstrated how double data is converted into float and int type.

There are several forms of type casting

In type cast, a cast operator compels the conversion of one data type into another in accordance with the requirements of the program. The cast operator comes in four different varieties in C++:

  • Static cast
  • Dynamic cast
  • Const cast
  • Reinterpret cast
static_cast < new_data_type > ( expression ) ;  //syntax of static casting

Example4: A program to show how to utilize a static cast

Let's make a straightforward example to demonstrate how to utilize the static cast of type casting in C++ programming.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;  
int main ( )  
{  
    // declare a variable  
    double l ;  
    l = 2 . 5 * 3 . 5 * 4 . 5 ;  
    int tot ;  
      
    cout << " Before using the static cast : " << endl ;  
    cout << " The value of l = " << l << endl ;  
      
    // use the static_cast to convert the data type  
    tot = static_cast < int > ( l ) ;  
    cout << " After using the static cast : " << endl ;  
    cout << " The value of tot = " << tot << endl ;  
    return 0 ;                                                                                     
}  

OUTPUT:

Before using the static cast:
The value of l = 39 . 375
After using the static cast :
The value of tot = 39
........................................................
Process executed in 2 . 11 seconds
Press any key to continue

Explanation

In the above example of a program in C++, we have demonstrated the method of utilizing static cast of type casting.

Dynamic Casting

Only class pointers and references can be converted from one type variable to another using the runtime cast operator dynamic cast. It entails that the casting of the variables is verified at runtime, and a NULL value is returned if the casting is unsuccessful.

Example5: A program to show how to utilize C++'s dynamic cast

Let's write a straightforward C++ application that uses the dynamic cast function.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;      
class parent  
    {  
        public : virtual void print ( )  
        {  
        }  
    } ;  
    class derived : public parent  
    {  
    } ;  
    int main ( )  
    {  
           // create an object ptr  
    parent * ptr = new derived ;  
    // use the dynamic cast to convert class data  
    derived * d = dynamic_cast < derived * > ( ptr ) ;  
    // check whether the dynamic cast is performed or not  
    if ( d ! = NULL )  
    {  
        cout << " Dynamic casting is done successfully " ;  
    }  
    else  
    {  
        cout << " Dynamic casting is not done successfully " ;  
    }  
    }  

OUTPUT:

Dynamic casting is done successfully.
........................................................
Process executed in 2 . 11 seconds
Press any key to continue

Explanation

In the above example of the program in C++, we have demonstrated the use of dynamic casting function which converted from one type variable to another using the runtime cast operator dynamic cast.

Example6: C++ program that makes advantage of the Reinterpret Cast

Let's create a program to show how to convert a pointer in C++ using the reinterpret function.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;      
int main ( )  
{  
    // declaration of the pointer variables  
    int * pt = new int ( 65 ) ;  
    // use reinterpre_cast operator to type cast the pointer variables  
    char * ch = reinterpret_cast < char * > ( pt ) ;  
    cout << " The value of pt : " << pt << endl ;  
    cout << " The value of ch : " << ch << endl ;  
    // get value of the defined variable using pointer  
    cout << " The value of * ptr : " << * pt << endl ;  
    cout << " The value of * ch : " << * ch << endl ;  
    return 0 ;  
}  

OUTPUT:

The value of pt : 0x5cfed0
The value of ch : A
The value of * ptr : 65
The value of * ch : A
........................................................
Process executed in 2 . 11 seconds
Press any key to continue

Explanation

In the above example of a program, we have demonstrated the conversion of pointer in C++ using the reinterpret function. This indicates that it does not verify if the pointer or the data it points to are identical.

Example7: A C++ program that use the Const Cast

Let's create a program that uses C++'s const cast function to cast a source pointer to a non-cast pointer.

#include < iostream > 
#include < bits/stdc++.h >
#include < stdlib >
#include < stdio > 
using namespace std ;      
// define a function  
int disp ( int * pt )  
{  
    return ( * pt * 10 ) ;  
}  
int main ( )  
{  
    // declare a const variable  
    const int num = 50 ;  
    const int * pt = # // get the address of num  
    // use const_cast to chnage the constness of the source pointer  
    int * ptr = const_cast < int * > ( pt ) ;  
    cout << " The value of ptr cast : " << disp ( ptr ) ;  
    return 0 ;  
} 

OUTPUT:

The value of ptr cast : 500
........................................................
Process executed in 2 . 11 seconds
Press any key to continue

Explanation

In the above example of a program in C++'s const cast function to cast a source pointer to a non-cast pointer. It implies that we have two options for doing the const: either changing a const pointer to a non-const pointer or deleting or removing the const from a const pointer.



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