Read or watch:

• stdarg.h
• Variadic Functions
• Const Keyword

• What are variadic functions
• How to use va_start, va_arg and va_end macros
• Why and how to use the const type qualifier

Variadic functions are functions that can accept a variable number of arguments. These functions can be very useful when you need to pass an unknown number of arguments to a function.

In order to use variadic functions, you will need to make use of three macros: va_start, va_arg, and va_end.

• va_start

The va_start macro is used to initialize the list of arguments. It takes two parameters: ap, which is a va_list type variable that will store the list of arguments, and last, which is the last named argument in the function.

void function(int arg1, ...) {
    va_list ap;
    va_start(ap, arg1);
    // rest of the code
}

• va_arg

The va_arg macro is used to retrieve the next argument from the list. It takes two parameters: ap, which is the va_list type variable that stores the list of arguments, and type, which is the type of the argument that you want to retrieve.

void function(int arg1, ...) {
    va_list ap;
    va_start(ap, arg1);
    int arg2 = va_arg(ap, int);
    // rest of the code
}

• va_end

The va_end macro is used to clean up the list of arguments. It takes one parameter: ap, which is the va_list type variable that stores the list of arguments.

void function(int arg1, ...) {
    va_list ap;
    va_start(ap, arg1);
    int arg2 = va_arg(ap, int);
    // rest of the code
    va_end(ap);
}

Variadic functions can be very useful when you need to pass an unknown number of arguments to a function. By using the va_start, va_arg, and va_end macros, you can easily work with variadic functions in your code.

In C programming language, const is a keyword used to declare a variable as read-only. This means that the value of a const variable cannot be changed once it is initialized.

The const variable is stored in the read-only memory (ROM) section of the program memory. This means that the value of a const variable cannot be changed at runtime and is guaranteed to be the same throughout the execution of the program

• Syntax

The syntax for using the const keyword in C is as follows:

const data_type variable_name = value;

• Example

const int num = 10;

In the above example, the variable num is declared as a const of type int and is initialized with a value of 10. Once initialized, the value of num cannot be changed.

If you try to modify the value of a const variable, the compiler will generate an error message.

Using const in your code has several benefits, including:

• It makes your code more readable and self-documenting, by indicating that the value of a variable will not change.
• It helps prevent bugs caused by accidentally modifying a variable that should not be changed.
• It allows the compiler to perform optimizations, which can result in faster and more efficient code.

In summary, the const keyword in C is used to declare read-only variables, which cannot be modified once they are initialized. Using const can help make your code more readable, prevent bugs, and improve performance.

#include <stdio.h>
#include "variadic_functions.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    int sum;

    sum = sum_them_all(2, 98, 1024);
    printf("%d\n", sum);
    sum = sum_them_all(4, 98, 1024, 402, -1024);
    printf("%d\n", sum);
    return (0);
}

$ ./a
1122
500
$

#include "variadic_functions.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    print_numbers(", ", 4, 0, 98, -1024, 402);
    return (0);
}

$ ./b
0, 98, -1024, 402
$

#include "variadic_functions.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
    print_strings(", ", 2, "Jay", "Django");
    return (0);
}

$ ./c
Jay, Django
$

#include "variadic_functions.h"

/**
 * main - check the code
 *
 * Return: Always 0.
 */
int main(void)
{
	print_all("ceis", 'B', 3, "stSchool");
    return (0);
}

$ ./d
B, 3, stSchool
$