/*
 * Simple example of array -- compute variance.
 *
 * Recall that we can get input from a file with "I/O redirection", e.g.,
 * 
 * a.out < in.txt
 */
#include <stdio.h>

/*
 * define size of array using preprocessor directive:
 * compiler will replace "MAXSIZE" with "10" in code below
 * (artificially low for testing)
 */
#define MAXSIZE 10

/* convenience function to square a number */
double square(double d) { return d*d; }

/* main program */
int main(void) {
	double sum = 0;
	double input;
	double a[MAXSIZE];

	/* read in values and compute average */
	printf("enter floating-point values (at most %d), anything else to end\n",
            MAXSIZE);
	int count = 0;
	/* keep calling scanf to read another value until it fails */
	while ((count < MAXSIZE) && (scanf("%lf", &input) == 1)) {
		/* 
		 * make sure we don't overflow the array 
		 */
        a[count] = input;
        sum += input;
        count++;
	}
	double average = sum/count;
	printf("sum is %g\n", sum);
	printf("average is %g\n", average);

	/* compute variance */
	double variance_sum = 0.0;
	for (int i = 0; i < count; i++) {
		variance_sum += square(a[i]-average);
	}
	printf("variance sum is %g\n", variance_sum);
	printf("variance is %g\n", variance_sum/count);
	return 0;
}