#include <stdio.h>
#include "fields.h"

typedef struct {
  IS is;
  int field;
} TokenGen;

TokenGen *new_tokengen(char *fn)
{
  TokenGen *tg;

  tg = (TokenGen *) malloc(sizeof(TokenGen));

  tg->is = new_inputstruct(fn);
  if (tg->is == NULL) return NULL;
  tg->field = -1;
  return tg;
}

char *tokengen_get_token(TokenGen *tg)
{
  char *s;

  while(tg->field == -1 || tg->field >= tg->is->NF) {
    if (get_line(tg->is) < 0) return NULL;
    if (tg->is->text1[0] == '#') {
      tg->field = -1;
    } else {
      tg->field = 0;
    }
  }

  s = tg->is->fields[tg->field];
  tg->field++;
  return s;
}

main(int argc, char **argv)
{
  int n, i;
  double *values;
  double avg;
  double variance;
  TokenGen *tg;
  char *s;
  
  /*  First you need to get <b>n</b> from the command line arguments. */
  
  if (argc != 2) {
    fprintf(stderr, "usage: variance3 n\n");
    exit(1);
  }
  n = atoi(argv[1]);
  if (n <= 0) exit(1);

  /*  Next, you need to <b>malloc()</b> space for <b>n</b> doubles.   */

  values = (double *) malloc(sizeof(double)*n);

  /*  Next, you read them in using the token generator */

  tg = new_tokengen(NULL);
  for (i = 0; i < n; i++) {
    s = tokengen_get_token(tg);
    if (s == NULL) exit(1);
    if (sscanf(s, "%lf", &(values[i])) != 1) exit(1);
  }
  
  /*  Next, you compute their average. */

  avg = 0;
  for (i = 0; i < n; i++) {
    avg += values[i];
  }
  avg /= n;

  /*  Now, you compute the sum of the squares of the differences. */

  variance = 0;
  for (i = 0; i < n; i++) {
    variance += ((values[i]-avg)*(values[i]-avg));
  }

  /*  Finally, you compute the variance and print them both out. */

  variance /= n;

  printf("Average:  %lf\n", avg);
  printf("Variance: %lf\n", variance);
}