/* Solution to 3rd question on Tutorial sheet for week 5 */

#include <stdio.h>
#include <stdlib.h>

/* The 'point' of this question is to get you to do a little 
 * bit of work with functions (even though its not absolutely
 * necessary to solve the problem).  We haven't done much
 * work on functions that return more than one item, therefore
 * in coming up with the function, we need to pass at least 
 * some of our solution through a parameter (which therefore 
 * must be in pointer form).  
 * Our choice is to have the return type of the function 
 * be double, and be used to return the mean of the given 
 * parameters.  Then we set up a parameter called sd, a 
 * pointer to a variable which will eventually store the
 * standard deviation.  */  

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

double stats(double *sdpointer, double a1, double a2, double a3) {
  double mu, sd;
  mu = (a1 + a2 + a3)/3;
  sd = (square(a1-mu) + square(a2-mu) + square(a3-mu))/3;
  *sdpointer = sd;
  return mu;
}


int main(void) {
  printf("\n");
  double a, b, c, mean, std;
  printf("Input three floating point numbers separated by whitespace: ");
  scanf("%lf", &a);
  scanf("%lf", &b);
  scanf("%lf", &c);
  printf("\n");
  mean = stats(&std, a, b, c);
  printf("The mean is %f and the standard deviation is %f.\n", mean, std);  
  return EXIT_SUCCESS;
}