#include <math.h>
#define M 5
float correlate();

main()
{
  int f[100]; int g[100]; 
  int gs,ge, fs, fe, n;
  int three, four, m;
  float num; 
  
  init_corr (f,g);
  
  printf ("gs?");
  scanf ("%d", &gs);
  printf ("ge?");
  scanf ("%d", &ge);
  printf ("fs?");
  scanf ("%d", &fs);
  printf ("fe?");
  scanf ("%d", &fe);

  n = ge-gs;

  four   = sum_funct (g, gs, n); 
  three  = sum_sqr (g, gs, n);
  printf ("three: %d", three);
  printf ("  four: %d\n", four);
  for (m = -M; m <= M; m++)
  {
    num = correlate (three, four, f,g, gs,ge, fs+m, n);
    printf ("=========================================\n"); 
    printf ("m: %d ----> correl_value: %f\n", m, num);
    printf ("=========================================\n"); 
  }
}

init_corr(f,g)
int f[]; int g[];
{
  int x;
  for (x=0;x<=45;x++)
  {
    if (x<8)
      f[x] = 0;
    else
      f[x] = x-8;
    if (x<4)
      g[x] = 0;
    else
      g[x] = x-4;
    /*printf ("f[%d]: %d", x, f[x]);
    printf ("  --- g[%d]: %d\n", x, g[x]); 
   */ 
  }
}

sum_funct (array, s,n)
int array[]; int s,n;
{
  int x;
  int sum = 0;
  for (x=s;x<= s+n;x++)
  {
    sum = sum + array[x];
  }
  return (sum);
}

sum_both (f,g, gs,ge, fs)
int f[], g[]; int gs,ge, fs;
{
  int x;
  int sum = 0;
  int ind;
  ind = fs; 
  for (x=gs;x<=ge;x++)
  {
    sum = sum + (f[ind] * g[x]);
    ind++; 
  }
  return (sum);
}

sum_sqr (array, s,n)
int array[]; int s,n;
{
  int x;
  int sum = 0;
  for (x=s;x<=s+n;x++)
  {
    sum = sum + (array[x] * array[x]);
  }
  return (sum);
}

float correlate(three, four, f,g, gs,ge, fs, n)
int three,four; int f[],g[], gs,ge, fs, n;
{
  int one, two, mt; 
  float numer, denom, first, second;
  float correl_value;

  one    = sum_funct (f, fs, n); 
  two    = sum_sqr (f, fs, n);
  mt = sum_both (f,g, gs,ge, fs);

  printf ("one: %d", one);
  printf ("  two: %d", two);
  printf ("  mt: %d\n", mt);
  
  numer = (float) (mt - (one * four)/n);
  first =  two - ( (one*one) / n);
  second = three - ( (four*four) / n ); 
  printf ("first %f second %f times: %f\n", first, second, first*second);

  denom = sqrt (first * second); 
  correl_value = (float)numer/denom; 
  printf ("numer: %f  denom: %f corr: %f\n", 
           numer, denom, correl_value);
  return ( (float)correl_value);
}