C program to find sum, max and min with Variadic functions

Variadic functions in C allow you to create functions that can accept a variable number of arguments. This is useful when you need functions like sum(), max(), and min() that can work with different numbers of input values. To implement variadic functions, we use the ellipsis (...) notation and include the <stdarg.h> header file.

Syntax

return_type function_name(fixed_parameter, ...);

The key macros for handling variable arguments are −

• va_list: Stores information about variable arguments
• va_start: Initializes the va_list to start accessing arguments
• va_arg: Retrieves the next argument of specified type
• va_end: Cleans up the va_list when finished

Example: Sum, Max, and Min Functions

Here's a complete implementation of variadic functions to calculate sum, maximum, and minimum values −

#include <stdio.h>
#include <stdarg.h>

int sum(int cnt, ...) {
    va_list ap;
    int i, n = 0;
    
    va_start(ap, cnt);
    for (i = 0; i < cnt; i++) {
        n += va_arg(ap, int);
    }
    va_end(ap);
    return n;
}

int min(int cnt, ...) {
    va_list ap;
    int i, current, minimum;
    
    va_start(ap, cnt);
    minimum = va_arg(ap, int); // Initialize with first argument
    
    for (i = 1; i < cnt; i++) {
        current = va_arg(ap, int);
        if (current < minimum) {
            minimum = current;
        }
    }
    va_end(ap);
    return minimum;
}

int max(int cnt, ...) {
    va_list ap;
    int i, current, maximum;
    
    va_start(ap, cnt);
    maximum = va_arg(ap, int); // Initialize with first argument
    
    for (i = 1; i < cnt; i++) {
        current = va_arg(ap, int);
        if (current > maximum) {
            maximum = current;
        }
    }
    va_end(ap);
    return maximum;
}

int main() {
    printf("Sum: %d
", sum(5, 5, 2, 8, 9, 3));
    printf("Max: %d
", max(4, 5, 9, 2, 7));
    printf("Min: %d
", min(6, 8, 5, 2, 6, 7, 9));
    return 0;
}

Sum: 27
Max: 9
Min: 2

Key Points

• The first parameter (count) tells the function how many variable arguments to process
• For min() and max() functions, initialize with the first argument instead of hardcoded values
• Always call va_end() to clean up the va_list
• Variable arguments are accessed in the same order they are passed

Conclusion

Variadic functions provide flexibility in C programming by allowing functions to accept variable numbers of arguments. They are essential for creating utility functions like mathematical operations that work with different input sizes.