/*
 * Program to compute variance of integers from stdin (example of using
 * array).
 */
#include <stdio.h>

/* make array size a named constant so it's easy to change */
#define ASIZE 100

/* "macro" -- compile-time function (compiler expands) */
#define SQUARE(x) (x)*(x)

int main(void) {
	printf("enter integers, anything else to stop\n");

	int nums[ASIZE];

	int n;
	int count = 0; /* how many elements have been read */
	int sum = 0;   /* sum of elements so far */

	/* read input and compute count and sum */
	while (scanf("%d", &n) == 1) {
		if (count >= ASIZE) {
			printf("too much input -- max of %d\n", ASIZE);
			return 1;
		}
		nums[count] = n;
		count += 1;
		sum += n;
	}

	/* compute average */
	double avg = (double) sum / (double) count;
	printf("avg %f\n", avg);

	/* 
	 * compute variance:
	 *
	 * average of sum of (nums[i] - avg)**2
	 */
	double vsum = 0.0;
	for (int i = 0; i < count; ++i) {
		/*
		printf("diff %f sq %f\n", nums[i]-avg, SQUARE(nums[i]-avg));
		*/
		vsum += SQUARE(nums[i] - avg);
	}
	printf("variance %f\n", vsum / count);
	return 0;
}