/*
 * compute variance of doubles entered as input
 */
#include <stdio.h>

#define N 10

double square(double x) { return x*x; }

double variance(void) {
	double a[N];
	int count = 0;

	/* read numbers into array */
	double temp;
	while ((scanf("%lf", &temp) == 1) && (count < N)) {
		a[count] = temp;
		count += 1;
	}
	/* FIXME nice way to print warning if we stopped because array is full? */

	/* compute average */
	double sum = 0.0;
	for (int i = 0; i < count; ++i) {
		sum += a[i];
	}
	double avg = sum/count;
        /* FIXME uncomment for testing?
	printf("avg %f\n", avg);
        */

	/* compute variance */
	sum = 0.0;
	for (int i = 0; i < count; ++i) {
                /* FIXME uncomment for tesing?
		printf("a[i] %f square %f\n", a[i], square(a[i] - avg));
		*/
		sum += square(a[i] - avg);
	}
	return sum/count;
}

int main(void) {
	printf("enter doubles, anything else to stop\n");
	printf("variance %f\n", variance());
	return 0;
}