Function Pointer as Argument in C

January 18, 2023

Function Pointer as Argument :

The function itself cannot be passed as an argument to another function.However, by utilising a function pointer, we can pass the reference to a function as a parameter.As the function parameter is supplied as a pointer that contains the address of arguments, this technique is known as a call by reference. .

Syntax :

(type) (*pointer_name)(parameter);

Example :

Run

#include<stdio.h>
//function to display even numbers
int help(void (*show)())  
{  
    for(int i=0;i<=10;i+=2)  
    {  
        show(i);  
    } 
    return 0;
} 
//printing the value
void print(int val)  
{  
    printf("%d ",val);  
}  
int main()  
{  
    void (*show)(int);       
    printf("The even values are :");  
    help(print);  
    return 0;  
}

Output :

The even values are :0 2 4 6 8 10

What Happened Above ? In the above Program, we write two function to help to find even number and print to print the numbers and use function arguments in the main function.

Pointers in C

Pointer to arithmetic in C

Null pointer

Function pointer

Pointer v/s array

Point to remember for Function Pointer as Argument in C :

Point to Remember If any change made by the function using pointers, then it will also reflect the changes at the address of the passed variable.

Example :

Run

#include<stdio.h>
// function to swap two integer
void help(int *a, int *b) 
{
    int temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

int main()
{
    int val1 = 15, val2 = 30;
   
    help(&val1, &val2);    //passing values to function
   
    printf("value of val1 = %d\n", val1);
    printf("Value of val2 = %d", val2);
    return 0;
}

Output :

value of val1 = 30
Value of val2 = 15

What Happend Above? In the above program, we swap two numbers using function pointer as arguments.

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Function Pointer as Argument in C